VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: fspGTD on August 31, 2004, 11:06:46 pm
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I got the head off my 1.6lTD motor... the one that I damaged by mis-shifting into 1st gear instead of 3rd gear during max acceleration while racing, causing the motor to be drastically over-revved.
The head looks like it won't be rebuildable, but I'm going to take it to my trusted machinist to see what he thinks. One lifter "bucket" was completely missing from where it should be, and instead there were shattered pieces all over. And another bucket was damaged and had a missing, shattered adjustment shim. The cam had some damage on the lobes that had the damaged lifter buckets / shims. All the intake valves, buckets, and lobes were fine, it was just the exhaust valves that had the damaged parts. The bores in the head where the lifter buckets rode in were gouged out, some pretty badly. It's because of that that I think the head may not be re-usable. I wish I had a digital camera with me earlier today so I could show you guys! I'll have to take some pics of it soon to show you guys the carnage.
Anyway, I also have some good news to offset the bad. My dad has a core 1.6lTD solid lifter motor, which we pulled the head off of today. The bottom end was trashed (melted pistons and every piston had deep recesses from what looked to be a mis-timed exhaust valves hitting them repeatedly) but it looked like the previous owner tried to save the engine by installing a freshened up or maybe even brand new head. The head looks to be in really good shape. I'm going to drop it off at my machinist's and have it checked out more closely.
More later on the bottom-end situation...
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The bores in the head where the lifter buckets rode in were gouged out, some pretty badly. It's because of that that I think the head may not be re-usable.
Ouch. I've been catching up on reading on the board over the past few days, and I was rather surprised to read about the over-revving incident. I'm sorry to hear about the damage.
If the lifter bores are messed up, then you've got a paperweight/conversation piece and not
much more I'm afraid.
Sounds llike your replacement head has potential though - I've got my fingers crossed.
{QUOTE]
More later on the bottom-end situation...[/quote]
Hopefully it's nothing more than a few dented pistons!
I had a solid lifter 1.6TD where the timing jumped and one of the lifters was driven right out of the bore, wehre it ended up getting wedged inbeween the cam lobe and the thin wall of the head casting, cracking it to the point where iit actually bulged out. Hydraulic lifters seem to sacrifice themselves for the good of the head, but there's nothing to give in the solid lifter engines, and it shows.
Drew
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I just dropped both heads off at my machinist... he's going to take a look at both and get back to me later. He actually said there might be hope with the over-revved head - that he might be able to install bushings in the messed up lifter bores. But one of them is really bad. It's probably gouged out up to 2-3mm sideways. That would need to be a pretty thick bushing. But this machinist is really good... he welded the cracks between valves on that head, and they did not re-appear... More info later on the bottom end!
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Any idea of what the rpm was, when it let go? Also, what do you think the mechanism of the event was? ie belt stretched/broke, valves lagging etc?
Hope you can get it back together for cheap.
m alexander
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There is more info about it on this thread:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=223&start=15
I can't really say for sure what the RPMs went up to, but it may have been up to 9000RPM.
The timing belt remained in tact. In fact I could even turn over the engine with the starter pretty well (must have been murdurous on the cam lobes with the shattered cam followers though :? )
From the engine being wound way farther than it should have been as a result of the mis-shift over-rev, it is likely that the valves floated, and then the pistons which "chase" the exhaust valves hit those exhaust valves, and then I can't really say what happened next.
There was also carbon/soot blown into the intake manifold, which made it's way back to the intercooler outlet!
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I was a motorcycle mechanic in a previous life... Old Kawasaki KZ900/1000cc engines used to do the same thing when badly over-revved. They used an identical "shim over bucket" type of valve actuation. When these engines floated the valves they generally flicked the adjustment shims out of the buckets. There wasn't enough room in the head for the shim to get clear of the cam so the damage was usually pretty severe. Most drag racers installed shim under bucket lifters and valve spring retainers from the KZ550/750. These carried a smaller shim in the top of the valve spring retainer under the "bucket". A better setup for rev-ability but the cams had to be pulled to set the valve clearance. For the VW maybe hydraulics would work better on a highly revved motor. They might be a bit heavier and float sooner but the consequences of valve float wouldn't be as severe...
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Yeah... I can see that happening! somehow, during the over-revving period, when the followers moved away from the cam lobes, the shims may have flown out of their buckets... and then yes, that could cause the shims and/or the followers to get shattered.
In greg Raven's "water-cooled volkswagen performance handbook", they mention there are the aftermarket solid followers available that do away with the shims (downsides are that adjusting valve clearances requires camshaft removal. :? ) Benefits according to the text are the weight gets reduced a lot - from 71 grams (stock shim and bucket) down to 43 grams (solid-top follower and lash caps), thus allowing the setup to revv higher without valve float. Doesn't matter a whole lot for my uses though - my race class don't allow deviations from stock equipment in this area.
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I got the junk head back from the machinist and took some pics for you guys - note the badly scored exhaust valve cam follower bores:
(http://www.imagestation.com/picture/sraid147/p0e391efa6aa0e73bd5b30453d2210ac4/f6280fdc.jpg)
(http://www.imagestation.com/picture/sraid147/pa938125f7f4547bba84b7c9aef0a5ad0/f6280fe1.jpg)
I also saw the progress of my new head rebuild at the machine shop. It is is coming along nicely. I'm having them port-match it to a long-runner A2 gasser intake manifold. 8)
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I got the junk head back from the machinist and took some pics for you guys - note the badly scored exhaust valve cam follower bores:
Well, I was expecting worse. How did the combustion chambers look? There is something to be said for the durability of these heads. :)
- A little off topic- any idea if those aftermarket solid followers are avaliable anymore?
I also saw the progress of my new head rebuild at the machine shop. It is is coming along nicely. I'm having them port-match it to a long-runner A2 gasser intake manifold. 8)
Nice. :D
It aught to run like a scared... er... Rabbit! :)
Brendan
84 Scirocco 8v
00 Camaro L36 M49
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Combustion chambers looked great - here they are, uncleaned:
(http://www.imagestation.com/picture/sraid147/pee7de663439203e88d5a00ae14b3a3b2/f6280fe0.jpg)
The cracks between the valves that the machinist repaired didn't even come back! He does good work. :P
I don't know about those one-piece cam followers.
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...and here is the long-runner A2 gasser intake:
(http://www.imagestation.com/picture/sraid138/p8d354668f707a80fdd27663778f89d77/f718ee6a.jpg)
Installing it will require relocating the turbo, which I don't have quite figured out yet. (But when I do, this intake will be all cleaned, port-matched, and ready to bolt on. 8) )
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Jake
How did the short block hold up?
m alexander
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Oh yeah - forgot to update you guys on that. Two of the pistons got dents in them. The dents are a little worse than last time it had piston-valve interference (which was when the timing belt got taken out, leading to bent valves and camshaft being broken into several pieces.) One piston just has minor and even depression across the entire face of the valve contact. You can feel it with your fingernail, but not very deep. The other piston, which got it the worst, got gouged a little more deeply at the side, which sort of looks like maybe the valve head got bent around and the edge dug in a little bit. I am going to try and smooth out the surface of the pistons (not sure exactly how yet.) And maybe bolt the rebuilt head and and see how the bearings held up. This bottom end isn't the first time it's been slammed into valves! It's amazing how well it held up and how well it ran since last time this happened. It will be sort of an experiment to see if the bottom end runs well, etc after bolting on the rebuilt head, knowing the RPMs that it's seen. It should make for an interesting experiment! If I wanted, I could also slip a set of new rod bearings in. I'm not sure if I should do that or not, I was going to ask my machinist what he thought. He said if I bothered to drop the pan and inspect them, I might as well go the whole nine yards and slip in some new rod bearings. I'm not sure if I'm even going to bother though. Like I said before, I know it's not seized. Seems to turn over pretty freely. And it has alread survived one valve bending eposide and seemed to run fine after that. What do you guys think, disassemble the oil pan and put new rod bearings in or just bolt the head on as-is and see how it runs? :P
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I say measure the piston protrusion to check for anything bent. If all's good, button 'er up! I would'nt even worry about the marks in the piston tops as long as crowns aren't dented bad enough to pinch the rings.
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Oh, they sure aren't dented that badly! And it's just in the middle where the valves are. When I get a new digital camera here soon, maybe I'll take some close-ups.
Good idea on piston protrusion measurements, Larry - I have protrusion measurements saved that were taken before the event, recorded individually for each piston. I could easily measure them now and see how close they were to before... if something is not close, I know that there would be major trouble (IE: bent rod or crank, or bearing severely squashed or missing...)
Although I'd have more confidence in just replacing those rod bearings, I sort of want to try it without doing anything to the bottom end if I can, just to prove to myself that these bottom ends are capable of taking extreme RPMs and surviving (or if they are not capable of that kind of abuse, finding out about it...) This current bottom end is totally a stock-spec kind of rebuild - no balancing, blueprinting or anything. So if that could take a 1st gear overrevv and keep on running well afterward, it would be saying a lot I think.
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Jake, I definitely vote with the "throw the head on it and go" crowd. In fact, I have done it myself, though not with a diesel. A while back my son had my Talon TSi up at Thunderhill for a driver's school when he dropped an exhaust valve head at about 7000 RPM. The Talon engine is an interference fit, so the valve head beat the heck out of the head and severely and repeatedly hammered the top of the piston.
Rather than pull the engine and do a proper rebuild, after consulting with my favorite mechanic I decided to install a replacement head and see how it ran (the engine turned over fine and the tops of the pistons all reached the same height within the limits of our measurements). On my mechanic's suggestion, I did take an air grinder to the top of the piston to smooth down the high spots and ensure there were no exposed sharp edges (to reduce the chance of hots spots developing into early detonation). I used a "fine" porting and polishing stone for the work -- which took me all of 5 minutes.
So far the car is running great (I've had it up to 6500 RPMs), passed California smog with no problems, and there is no sign yet of knock.
I say go for it, Bro! ;)
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Here's a test of my new digital camera - a close-up pic of the carnage in the over-revved head...
(http://www.imagestation.com/picture/sraid147/p7950072b1dab8ff971bbfee5e319f4f2/f6280b69.jpg)
[edit: replaced picture with more reasonably sized, lower-res version]
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More to update along these lines... Last night I measured my piston projections. I got, from #1 - #4, protrusions at the exact center of the pistons being approx .025", .022", .025", .021". Previous measurements that I have on file (measured before the over-rev incident) were .022", .018", .0225", .0175". So with the later measurement the piston project more by +.003", +.004", +.0025", +.0035".
Now two observations about these sets of measurements... it doesn't make much sense for the pistons to project farther now than they used to, the later measurements were probably because I measured a different spot on the piston or varied the measuring technique somehow. Ther are on average about 3 thousands more projected in the later measurements, which is pretty darned close and probably within my margin for error of the two measuring techniques. Comparing the differences of the latest measurements to the previous, it it encouraging that they are tightly clustered, within one and a half thousands of each other.
This information is a good sign I'd say, and it suggests that my bottom end is fine and didn't sustain internal damage from the over-revv incident (IE: the rods didn't get bent, or bearings didn't get mashed out of place when the pistons hit the valves.)
By the way, the worst valve damage on the piston top is #4, although all the other cylinders looked like they kissed the valves at one point or previous incident (when timing belt broke.) I am working on cleaning the cylinders and piston tops, and am using a razor blade to shave off the high aluminum spots and the bulk of the carbon build-up on top of the piston... I've got two more pistons to clean, then I'll post more pics!
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Nice work Jake... I am new here and must say, from reading the archives, your work has been an inspiration. I just wonder, don't you have any plans of raising boost again?
I've found uncoated piston tops or any other carboned up part are easily cleaned with a combination of scotch brite and a solvent (like gasoline or perhaps diesel). One does not work worth a damn without the other, but together they work wonders. Of course you scrape off the bulk first.
Instead of scotch-brite (which I found in body shops, used to ever-so-slightly rough up old paint before spraying over it) you can use those slightly abrasive cleaning pads you may find in the kitchen. Clean up the shavings well though, you don't want your bores "scuffed clean" as well.
Marcel
(Who has also found a bit of extra useable powerband now. Not nearly as much, but a good start indeed.)
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More pics! 8)
Are you getting another head in order?
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Marcel - thanks for the compliments. :D I won't be raising boost pressure, because my race class (Street Prepared class, SCCA Solo 2) requires an unmodified wastegate... but, I've got plenty of other things left to experiment with to try and get more power, and it's surprising how far this little IDI diesel has come already on stock boost (not to mention stock cam, and stock head)!
That scotch-brite method does well (I've used it before)... I use scotchbrite sponge cut into squares, as I found the sponge holds some solvent and delays the release of the solvent so you can scrub longer before it completely evaporates.
I've got the piston tops fairly clean, IE: surfaces are flat and all the big chunks of carbon scraped by razor blade off... I'm not sure if I'm going to sweat scouring off every little last bit of carbon - maybe! There was a touch of it on the top of one of the cylinder walls I wanted to attack before putting the head on, might need to break out some scotchbrite for that. Solvent and paper towel was not working very well.
TurboDS - I've got a new, freshly rebuilt head here in the garage, ports matched to manifolds, still wrapped up in plastic, ready to go. I even measured valve face recess on it (not sure where I put the measurements... but I do remember calculating that the CR varied as a result of varying valve recesses from one cylinder to another by no more than .1 )
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OK - on request - here's an image of the piston tops following the over-rev incident that I stitched together (no my engine isn't some sort of weird off-balanced thing where all pistons go to TDC simultaneously! :wink:
(http://www.imagestation.com/picture/sraid147/pda055161547be08bec6edb6bf8417149/f6280a55.jpg)
The piston tops as pictured have been scraped clean with a razor and the high edges of aluminum has also been shaved off with the razor. The worst damage was the exhaust valve groove pounded into piston #4 (at far right.) These pistons have had piston-valve contact twice. The first time was a broken timing belt (which really didn't mar into the pistons too deeply, IE although the valve contact is visible, it's hard to even feel it with your fingernail), and this latest time was the over-rev incident (some exhaust valves hit pretty good, especially #4 at right, sort of "dug in" sideways a bit as I suspect the valve bent sideways slightly as it happened...)
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Marcel - thanks for the compliments. :D I won't be raising boost pressure, because my race class (Street Prepared class, SCCA Solo 2) requires an unmodified wastegate...
Ah, right. Figured it had to be something like that. Still even for a streeter a good idea to get as much as you can without upping the boost, and THEN add more boost to the equation. Much better results than just upping the boost. (well, that's how it works for gassers, and I suppose it's no different for diesels!)
Marcel
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BTW those pistons have certainly received quite a beating... you sure you're not going to pull the pan and inspect the rod bearings (at least #4)even though piston protrusion seems ok?
Something I'd recommend for a gasser in a similar situation anyway (where my experience lies).
Sure, it's a messy job but for peace of mind... bearings are cheap, too, although it's probably better not to mess with them if they're allright.
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Last time I had piston-valve contact on this motor (resulting in bent valves and the camshaft breaking into several pieces!), I didn't change any bearings in the bottom end, and it seemed to run just fine! Oil pressure was good, etc. Especially since I don't have any evidence that the the pistons are projecting less now than they were before, and the bottom end rotates nicely and freely, and there has never been any oil starvation, I'm inclined to just bolt the head on to the block as-is. (Eventually, the plan is to get a blueprinted, full-rebuilt bottom end to replace this beaten one with... but nurse this one for at least a season longer!)
Oh yeah I thought it would be also a good experiment for the good of the GTD board readers to see how well the bottom end of a 1.6lD runs after having reached probably 8-9+K RPM! (IE: we'll see what kind of RPMs they are built to really take. ;) )
I also wanted to mention that the way I've shaved the pistons clean with a razor while not scrubbing them 100% clean emphasizes even the tiniest marks (for example, notice how clearly you can see the radial marks in the piston tops, which were from when the piston were tuned at manufacture, or how apparent the number stamped into the surface, also done at manufacture, are.) Many of these marks show up very clearly here in this picture, but you would not be able to feel them (or would only barely be able to feel them) with your fingernail - including some of the valve contact marks. Really the only significant depressions are where some of the exhaust valves hit, everything else is very minor.
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... emphasizes even the tiniest marks (for example, notice how clearly you can see the radial marks in the piston tops, which were from when the piston were tuned at manufacture...
Good point. It probably does look a lot worse on the picture than it is.
I still fear that the huge forces involved in leaving even a slight "impression" would also break through the bearing oil film, but time will tell. If it runs OK it's probably fine. Also it's not like you can't change rod bearings with the head on, so it's not really important at this stage.
Marcel
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Synthetic oil has got to only help in situations like this! Also the way I think the VW bottom end was designed (beefy, big bearing surfaces, etc) can only help too!
Question for you - if I just slap the head on there and it turns out that the rod bearings were bad... what would happen? Would it be rod knock noise that develops? Thanks...
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Yes, you could get an audible rod knock if the bearings are damaged. Also, if you have oil pressure and/or oil temp gauges, watch for substantial changes in their behavior since the "incident".
Absolute pressure/temperature readings usually don't mean much, but changes in their behavior can allow you to spot a bearing problem early (greatly reducing the risk of crankshaft damage).
I once had an engine that ate a set of brand new rod bearings in just 20 miles. It didn't even knock although the bearings were down to the backing metal in just 20 miles. I tore it down the 2nd time after the bearing job because it felt sluggish and exhibited high oil temps / lowish pressures after the bearing job. Indicating high friction (and likely excessive clearance). I have NO idea why it never knocked, I consider it one of those exceptions every rule seems to have... Turns out the root cause was an oil supply problem. Live and learn ;) But that's beside the point, just an extreme example of gauges being a Good Thing.
Don't let me scare you though ; as you say, likely the VW diesel bottom end is very strong.
Marcel
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I scoured clean the piston tops today - here's #4 with the worst of the valve damage:
(http://www.imagestation.com/picture/sraid146/p3df5a78438c03381df636d630979875e/f64f5763.jpg)
The valve damage on most of the other pistons I could indeed only barely feel with my finger or with my fingernail, so I'm not worried about any of those. This #4 piston however (pictured) is the one that I am most worried about.
you can see I prepped it for dremel grinding action... then I ground out some metal where it was pushed from the valve into the right "cloverleaf" swirl pattern...
(http://www.imagestation.com/picture/sraid146/pffeff2aaa614a74e59b8e1602a44759e/f64f575d.jpg)
And to wrap off the pics, here's one of the perfect blueprinted factory head, patiently awaiting installation... 8)
(http://www.imagestation.com/picture/sraid146/p35aaaff82edf04732656953a3664e359/f64f5756.jpg)
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IT'S ALIVE!!!
(http://www.imagestation.com/picture/sraid147/pe8368041779245ed0f6b7e9c378da222/f63bae05.jpg)
I got the motor running today! There is a coolant leak at the front water nipple I'm going to have to tend to before I can drive it, also need to change the cam break-in oil out soon, and flush the coolant... but it's getting close, and it sounded pretty good when it ran too! :P
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Lookin' good, Jake! :D
Could you post a close-up of the lower left corner of the pic immediately above? I'd like to see more deatils of the turbo air inlet.
Thanks! Stan
PS - I got a Bandwidth Exceeded msg for the photos above the latest one...
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Looks like I need a new image hosting provider. :? Got any ideas?
I could just use good ol' Imagestation, but the problem with them is that they will hose out only small images, so I can't really show the details captured by new high-res digital camera.
Stan, there are some pics of that air filter setup in this old hostboard thread... (Let me know if you want me to take shots of any other views.)
http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=291
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Congrats!
If you know how to use FTP for uploading, I can set you up some image-space on my webserver.
It's not very fast, but for posting a couple pics to this forum it should do just fine. (that's what I use it for anyway, posting pics to various forums)
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Thanks Jake, I'll check it out tonight. (The LAN-Nazis at work block Hostboard as "Chat".)
But they don't know about vwdiesel.net... :lol:
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Yes, you could get an audible rod knock if the bearings are damaged. Also, if you have oil pressure and/or oil temp gauges, watch for substantial changes in their behavior since the "incident".
Absolute pressure/temperature readings usually don't mean much, but changes in their behavior can allow you to spot a bearing problem early (greatly reducing the risk of crankshaft damage).
I once had an engine that ate a set of brand new rod bearings in just 20 miles. It didn't even knock although the bearings were down to the backing metal in just 20 miles. I tore it down the 2nd time after the bearing job because it felt sluggish and exhibited high oil temps / lowish pressures after the bearing job. Indicating high friction (and likely excessive clearance). I have NO idea why it never knocked, I consider it one of those exceptions every rule seems to have... Turns out the root cause was an oil supply problem. Live and learn ;) But that's beside the point, just an extreme example of gauges being a Good Thing.
Don't let me scare you though ; as you say, likely the VW diesel bottom end is very strong.
Marcel
OK... I've taken the engine through about 3 heat cycles now, and driven it around the street a bit. The good news: it rips! It really seems to like this new head. Power in the high RPMs seems really good (I haven't red-lined it yet, just trying to get a feel for the new performance of the motor.) Really goes like a "buzzsaw" at high rpms. I think this head might be a little bit of a better casting than the old one. I also set the intake cam shims a little tighter to get a little more lift. :)
The bad news: idle oil pressure when hot is lower now, vs compared to before the over-rev indicent. Before the incident I used to see about 1.8 bar hot idle oil pressure... now I'm reading closer to about 1 bar, almost half the old reading. The weight of oil is the same, and oil temperature is the same, so now I'm suspecting some bearing(s) got prematurely worn from the over-rev incident.
So considering what Marcel had to say, I'm thinking about pulling the pan and inspecting (and replacing if needbe) the rod bearings. Do you think I should worry about the main bearings as well, or is it likely that only the rod bearings got pounded? Also, what are the good brands of bearings I should look for? After I get a bearing removed, will I be able to see stamped on the back of it or something, what the undersize spec of it is in case I need to buy a replacement, so I can duplicate the spec? When inspecting the crank, should I be just looking for a gleaming bearing surface that is free of any bearing metal being stuck to it?
PS - I am not hearing any noises that seem really unusual. If there are any new unusual noises like rod knock, they must not be very loud. Also, the oil pressure at high RPMs is good.
PPS - I plan on abusing this bottom end (IE: winding it above 6k RPM), so what would you guys advise. I'd prefer to make the bottom end reliable if that is possible. Are the rod fasteners re-usable?
Thanks!
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Congrats!
If you know how to use FTP for uploading, I can set you up some image-space on my webserver.
It's not very fast, but for posting a couple pics to this forum it should do just fine. (that's what I use it for anyway, posting pics to various forums)
I fixed the broken image links (just using imagestation for now) thanks...
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Idle rpm is the same? (just eliminating...)
There's always a possibility the "new" head is using more oil pressure than the old one, but this lower idle oil pressure would worry me enough to at least check the rod bearings.
Just plastigauge one, two or all of them, starting with the worst (and block the crankshaft somehow while you do that, cos if it turns while tightening, it may smear the plastigauge and throw off your reading). Plastigauge should be applied dry ; it is a wax-like substance that does not like oil. Put oil back on after wiping off the plastigauge.
If the rods are OK, most likely so are the mains. Rod bearings nearly always die first. Mains are harder to plastigauge properly so if the rods are fine, it's not worth the effort to look further. Fasteners are reuseable but obviously mind the proper torque procedure both when plastigauging and on reassembly.
On the crankshaft, if in doubt, wipe off the oil and look for wear marks of any kind. Ideally the journals should be polished shiny. Minor scratches don't hurt, but a generally dull surface or blueish "heat marks" are bad.
The bearing surface should look nice and smooth, dull grey. Be careful with them, the layer that meets the crank is soft enough to scratch with a fingernail.
Bearings are best changed all at once (that includes the mains) so if it ain't broke, don't fix it ;)
Marcel
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Jake--with an oil pressure drop like that I would indeed recommend at least taking a look at things. As Marcel said, all would have to happen at once pretty much or else it would not make much sense to do it at all. If the bearings got mashed badly enough to cut your oil pressure in half, chances are the rod upper bearings and the lower crank bearings were both pretty screwed up.
However, I'm not sure you need to pull the pan yet if more testing can be done. Do you have an A2-style oil filter housing with the oil pressure or temp sensor on the top as well as the A1-style head-mounted sensor? Do you have pressure readings for both from your old engine? I don't know the VW lubrication system well enough to know for certain whether or not this will be possible, but maybe you could localize the pressure loss by taking pressure readings at both the head and the filter housing. If you're good at the filter housing but have low oil pressure at the head, I'd be pulling the cam cover rather than the oil pan. Also, like I said, if you happened to have readings from the motor before the over-rev, you could find where the change was.
BTW, who is this machinist who can cure the 1.6 head crack problem? I will be pulling the head off my motor later this week and will probably at least want to have it checked for warpage and pressure-retention, and if it has the cracks I may want them welded up too. There have been yays and nays with regard to shaving these heads; what's the opinion here? Bentley says it will ruin them, but I and many others see no particular reason a careful decking would be a problem.
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Jake--with an oil pressure drop like that I would indeed recommend at least taking a look at things. As Marcel said, all would have to happen at once pretty much or else it would not make much sense to do it at all. If the bearings got mashed badly enough to cut your oil pressure in half, chances are the rod upper bearings and the lower crank bearings were both pretty screwed up.
Well that's a bit pessimistic, and remember we're only talking idle oil pressure (doesn't take all that much to affect that). Probably pulling the pan is quicker and more certain than anything else now.
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Thanks for the info, guys... Yes, idle RPM should be and according to my memory is the same since the incident... haven't done any fuel injection changes since before or after the incident, and I don't recall noticing that it was lower (I do have a tach reference.) I don't drive this car regularly, but probably will drive it again for another test run fairly soon and will continue to monitor the oil pressures and will take a close look at the idle RPMs. It seems like if the problem worsens, that chances are that I will get a sign - IE: oil pressure will drop further, and/or I will hear a warning noise, such as a tapping or knocking develop.
I will consider the plastigage test, although I don't have it and haven't used it before. I also am not sure how much I trust it (after running out of oil from a broken aluminum oil pan, mom's Golf TDI got it's bearing clearances OK'ed from the VW dealer - I think they used a plastigage test - and then a few weeks later the engine developed a ticking noise and seized! The dealer screwed up their diagnosis somehow... :oops: ) If I do plastigage the rod or main bearings though, where do I position the plastigage on the journal, and how should the crankshaft be oriented when taking the measurement(s)?
Are you sure that since the rod bearings go first, it might not be a better strategy to just replace the rod bearings if I get as far as dropping the pan and pulling the conrod caps off to inspect them (rod bearings also turn are are pretty cheap for a set... only about $20.) I'd really love to not have to remove the tranny and drop the crankshaft to replace those mains!
v8volvo - I don't have record of oil pressures taken before the over-rev accident at the oil filter flange; only from the head. The machinist I have used for my last couple head rebuilds is Jerry at Northwest Connecting Rod Service - 1705 S 93rd, Seattle 206-763-2487. He seems to do good work at reasonable prices, and also seems very familiar and knowledgeable about VWs and VW diesels in particular. Surfacing the head seems to work OK if the pre-chamber inserts get surfaced properly along with the head (which is apparently a big stumbling block for a lot of machinists when attempting to do this job.) Also if too much material is shaved off the surface, it might give it a greater tendency to warp (either temporarily or permanently) in the event of an overheat, so that the headgasket seal between block and head would be compromised.
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Could it be as simple as the blow-off valve on the oil pump? Rat407 rebuilt his engine and still didn't have oil pressure...I'm not sure if he figured that one out or not.
Steve
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I see what you mean about dropping the crank (it's often easier to pull the engine in those cases... so you won't have to work upside down the whole time). BTW in many engines it's possible to remove the bearing caps one by one and replace main bearings without removing the whole crankshaft. You need a little trick to push the upper shell out and in, but it can be done. You still don't want to, though. Which is why I recommend leaving them ALL in if they're allright. If you want to replace the rod bearings only that's fine, but you still need to measure them, so you know whether to look at the mains or not.
Plastigauge is thin wax "wire". Comes in a few thicknesses, at about $1 per ~1ft strip. You take off a bearing cap, clean up, take (cut) about 1/2" of plastigauge, and put it on the crankshaft (when working under the car, you would put it in the bearing cap). It is used across the width of the bearing (parallel to the crankshaft). Put the bearing cap on, torque to spec, remove, and measure how thick the now squished strip has become compared to samples printed on the packaging.
If there's a lot of side clearance on the conrod, try to keep it from moving around as you tighten it. Crankshaft orientation does not matter as long as it is fixed in that position, so just pick a convenient position for each measurement. And mind the oil feed hole, you don't need plastigauge in there ;)
The only way to screw up is squishing/smearing the stuff too much by allowing things to move around or putting too much pressure on the bearing cap somehow. The stuff should be squeezed to the exact clearance and no further. This may be what went wrong on mom's car, or there might have been a completely different reason why bearing failure still ended up happening. If in doubt, measure twice and see if your results are consistent. Do not average, the highest reading is best, you can only err to the small side.
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Could it be as simple as the blow-off valve on the oil pump? Rat407 rebuilt his engine and still didn't have oil pressure...I'm not sure if he figured that one out or not.
Steve
Steve - I'm almost certain the oil pump is not to blame as I haven't touched the oil pump since the over-rev incident, and can't see it being damaged as a result of the incident... no sign of any metal particles entering the oil pump screen, IE: the pump pickup screen was totally clear.
At least it seems I still have more oil pressure than Rat407 ;)
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BTW in many engines it's possible to remove the bearing caps one by one and replace main bearings without removing the whole crankshaft. You need a little trick to push the upper shell out and in, but it can be done. You still don't want to, though.
That's incredible... wow. That sounds like a tricky job! And you're right sounds like something I'd much rather not risk if I don't have to!
Which is why I recommend leaving them ALL in if they're allright. If you want to replace the rod bearings only that's fine, but you still need to measure them, so you know whether to look at the mains or not.
Thanks for clarifying this. Makes sense to me that either all the mains would need to be replaced at once or none at all, or else the fresh, tight main bearings would probably wear prematurely.
Plastigauge is thin wax "wire". Comes in a few thicknesses, at about $1 per ~1ft strip. You take off a bearing cap, clean up, take (cut) about 1/2" of plastigauge, and put it on the crankshaft (when working under the car, you would put it in the bearing cap). It is used across the width of the bearing (parallel to the crankshaft). Put the bearing cap on, torque to spec, remove, and measure how thick the now squished strip has become compared to samples printed on the packaging.
If there's a lot of side clearance on the conrod, try to keep it from moving around as you tighten it. Crankshaft orientation does not matter as long as it is fixed in that position, so just pick a convenient position for each measurement. And mind the oil feed hole, you don't need plastigauge in there ;)
I was thinking if the bearing is worn egg-shaped, the plastigage even if torqued down carefully without movement might not detect the max wear if it wasn't oriented right. So if it was predictable where the wear would be, then I was thinking the crankshaft orientation and position of plastigage on it could be determined. However, I'm not sure what forces were more likely to have caused bearing wear - IE: high centrifugal force from the overrev (peaking at TDC between exhaust and intake stroke; pulling "up" on the piston/rod), or damage caused by the piston valve interference would be approaching TDC but would be in a downward direction on the piston/rod.
The only way to screw up is squishing/smearing the stuff too much by allowing things to move around or putting too much pressure on the bearing cap somehow. The stuff should be squeezed to the exact clearance and no further. This may be what went wrong on mom's car, or there might have been a completely different reason why bearing failure still ended up happening. If in doubt, measure twice and see if your results are consistent. Do not average, the highest reading is best, you can only err to the small side.
Yeah you're right, mom's car failure isn't really conclusive proof that plastigage doesn't work, I could just be over-reacting. There may have been another problem that they didn't diagnose the problem with it correctly. I hopefully will find out the story about what happened with that motor soon.
You're talking me into the plastigage. I'm going to drive the car some more first, and double check the low oil pressure condition exists and then if it still seems there is a problem, I'll get some plastigage and plan on dropping the pan to check them out. I am recalling now sometimes after driving the car very hard, seeing alarmingly low oil pressure at hot idle, IE: lower than normal even. I need some more driver's seat time to verify the oil pressure isn't up to par, I think.
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The one thing that comes to mind with mine is the head. From reading all the maintenance reciepts in the glove box from the PO there was annotations on some of the maintenance reciepts for when they had the alternator replaced and then again when they had the oil changed as well as the exhaust worked on that the oil light would flicker on. This was only on the reciepts of maintenance done after they had a new head put on due to the timing belt breaking and trashing the head. This was at 105k miles on the engine.
So I'm wondering, since I didn't mess with the head other than to make sure it was flat and had it pressure checked to make sure the valves sealed, that my problem is somewhere in the head. It would only make sense since the bottom half is all new with the bearings installed are to specification to include the intermediate shaft bearings. It is also the second oil pump, since it was easy to change I figured that might be my oil pressure problem. Once I get some funds built up and my garage built, the head is coming back off and I'm going to go completely through it and make sure the cam saddles are not worn out of limits. I got a ton of volume, just 0 pressure at the head port. So far I have 5k miles on the engine and the thing runs great. Just for now it is going to be a while till the money issue comes back to the GREEN level. With Christmas it might be a while. :( At least by then I will have a garage to work on it and can leave it without worry of massive dirt/dust blowing around the open engine, like it would in the car port.
I'm running straight 30w now and this morning with the temp at 30F the oil pressure at the head hit a wapping 24psi, then it warmed up and went to ZERO. I can say this much, you kind of get use to the blinking red light/buzzer going off after a while.
My latest trip to the salvage yard I came across an 86 NA diesel Jetta and on the dash was a strip of black electrical tape over the warning lights. I wonder how long they drove it that way.? :shock: The engine looked in good shape and everything was on it so, here in a day or so I'm going in and getting all I can off it.
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There's a great episodic journey on www.vwdieselparts.com about a guy changing the bearings with his engine in place. If you do a search it will be the post with 7 or more pages. :) You have to beat the transmission with a chisle to get the rear mains out but other than that it's supposed to be easy.
Steve
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Steve (Thanks for the tip) - A HA! I found it: http://www.vwdieselparts.com/forum/viewtopic.php?t=1747&postdays=0&postorder=asc&start=45
(Wow, these forums look pretty similar to vwdieselparts's. Even the "look and feel". Hmmm... hey even the users there look familiar! )
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I was thinking if the bearing is worn egg-shaped, the plastigage even if torqued down carefully without movement might not detect the max wear if it wasn't oriented right. So if it was predictable where the wear would be, then I was thinking the crankshaft orientation and position of plastigage on it could be determined. However, I'm not sure what forces were more likely to have caused bearing wear - IE: high centrifugal force from the overrev (peaking at TDC between exhaust and intake stroke; pulling "up" on the piston/rod), or damage caused by the piston valve interference would be approaching TDC but would be in a downward direction on the piston/rod.
I think it will. This egg shaped bearing wear will always allow some extra play (some up / down play, no matter which shell is damaged). Plastigauge measures free play, so no matter which side you put it, it will "see" the damage. Near the bottom of the bearing cap is probably the best place. BTW, like the other thread said, plastigauge is best cleaned off with a solvent.
I am recalling now sometimes after driving the car very hard, seeing alarmingly low oil pressure at hot idle, IE: lower than normal even.
That can happen as oil temperature rises. Very hard driving or extended high-speed driving would do that. Oil gets thinner, pressure drops. Is normal, although the difference should be small and pressure should not drop to alarming levels. May I recommend an oil temperature gauge? I generally put one on anything that's driven hard. It tells you SO much more than a water temp gauge can.
Marcel
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May I recommend an oil temperature gauge? I generally put one on anything that's driven hard. It tells you SO much more than a water temp gauge can.
Marcel
Already got one. Thanks for all the info, I don't have anything new as a yet to report but will post up here again as soon as I do.
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An update on the GTD... Although the engine seems to have decent power and drive well when the car is running, the engine has been really hard starting ever since putting on a rebuilt head on it since the over-revv incident. In fact I've only mustered the will to start it maybe 3 or 4 times. Initially I had to use all the tricks: block heater, lots of glowing, jump starting, and lots of cranking. Not happy with the performance of the A2 lightweight gear reduction starter I was using ever since I bolted it on, I rebuilt it, finding and fixing a 2.5 volt drop across the solenoid. So after fixing that it noticeably boosted cranking RPMs. But this was still not enough... the engine still required jump starting and lots of cranking before it would start.
So I borrowed a compression tester, and today I hooked it up and got some readings. Cranking speed during the compression test was 190 rpm, which is good I think.
1st pass:
320 psi
320 psi
340 psi
320 psi
2nd pass, after adding a tablespoon of oil in the cylinders, as recommended a VW diesel service training manuals...
620 psi
630 psi
605 psi
605 psi
Now this is kind of odd. I was kind of expecting if one of more valves weren't sealing, that I would have seen low compression on one or more cylinders, but not uniformly low. Also, I wouldn't have expected compression to virtually double after adding oil. That would seem to indicate rings. Do you guys agree?
Any of you had luck with the "wet" compression tests on these VW IDI diesels? Are the results conclusive? I noticed that some of the oil got up into the compression tester. And then it would spray out as a mist when I moved on to the next cylinder. What's preventing the oil from sealing a valve? Is this "wet" compression test really conclusive?
My engine builder suggests since to work on the bottom end I'd have to take the head off anyway, that if I take the head off I might as well bring it down to them and they'll vacuum test all the rings to make sure that the valve sealing is completely ruled out as the potential problem. (They would do this for free for me, since I had them rebuild the head.)
But, are there any diagnostic steps I should be doing before taking the head off?
I am thinking there may be some bottom end work in my future! :?
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I've heard good things about leak down tests.
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It definitely looks like you,ve got some bottom end problems Jake.Someone please correct me if I'm wrong but last time I looked in the Bentley I think It specifically stated not to do a wet compression test on the diesel just gas only and it said to preform a leakdown test instead .I'm not quite sure why the "wet test" is not recomended so mabye someone else could fill us in on why.
On another compression related issue I've just done a compression test on two 1.9tds and a 1.6td and at first I thought I would pull the #3,4 glowplugs and get the two readings from those cylinders to get a rough Idea on the engines condition without pulling the injectors and checking all four cylinders.So on the 1.9TD #4 cyl was at 350psi after 5 crank revotutions.So anyways I needed to check all four cylinders regardless and the reading through the injector adaptor on the same cylinder was now 400psi after the same 5 cranks.Obviously the different numbers were due to the fact that the glowplug compression adaptor does'nt have the glow plug's element on it that would normally be in the head Thus lowering the compression.So basically If anyone out there is checking compression through the glowplug hole you will need to add another 50psi almost exactly to your reading for it to be correct.I just thought I would add that incase anyone checks the compression using glow plug adaptors on any IDI diesels :wink:
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This is just a guess, so take it as such. I would think that doing a wet compression test on any diesel would not be a good idea. Obviously the fuel is off, but could it not theoretically try to start on the oil. Also having the oil in the cylinder would reduce the volume of the combustion chamber. It has been my experience that a leak down test will usually give the best answers, but I have only ever done them on gas engines.
Also Jake, it is my understanding that the engine requires 600 or so RPM for starting purposes, so I would think it would deem neccessary to reach the same speed during a compression test also. Somebody correct me if I'm wrong, but 190 RPM seems way to slow.
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I've heard good things about leak down tests.
:?: This is the compressed air test?
How do you differentiate between ring leakage and valve stem leakage?
DUH.. Of course it won't reach valve stems but will come out of intake and or exhaust. Or just valve cover. :roll:
Jake. What ever your problem is; its very 'even'... what are the chances of equally distributed valve leaks?
Could it just be even wear on the bores?
Mark-The-Miser-UK
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Hey guys - you bring up some good quesitons.
Regarding wet compression test - no bentley does not state you can't do it. In fact, it explicitely states you can. According to my bentley (covering '77-'84 Rabbit / Jetta Diesel) it states: "To determine whether the piston rings are causing low compression squirt a small quantity of SAE 40 oil into the low-reading cylinder(s) through the injector hole(s), and repeat the compression test. ..."
Furthermore, also in the VWoA service manual distributed to dealerships titled "Four Cylinder Diesel 1977-83 / ProTraining" (someone uploaded it here: http://www.vwdiesel.net/phpBB/viewtopic.php?t=321 ) gives compression test procedure on page 53, stating "A low reading can be rechecked by adding 1 tablespoon of engine oil through the injector hole..."
Also more about the wet compression test, the way I measured the quantity of oil to add was found a good spoon to use, then measured that 3 spoonfuls of water was equivalent to 1 tablespoon. If I put in 3 full spoonfuls, a bit of oil would get up into the compression tester. If I put in 3 light spoonfulls, not oil would get up into the compression tester. But I would imagine it would be thrown around inside the combustion chamber and no doubt, would add some to the compression ratio. The compression tester I used did it's measuring through the injector hole. It is very similar to the one pictured in the Bentley manual referenced above, on page 10. The glow plugs were left installed.
Moonstone - Regarding adequate cranking RPM - 600rpms is way above what is required for our motor and what our starter motors are capable of without any cylinders firing to assist. See same source referenced above (Protraining), where it states to check for adequate cranking speed on page 25: "Cold cranking speed must be at least 150rpm." (This is referring to standard cranking speed where all four cylinders have resistance during compression of course, not speed during compression test when only one cylinder has full compression loading, however I didn't really notice the RPMs seeming to be much different between the two.) I just can't see there being a problem with my motor's cranking speeds. The way I measured cranking rpms during the compression test was by counting the number of "puffs" on the compression gauge in a 10-second period, and multiplying that number times 12 to get the RPM of the crankshaft. 16 puffs in 10 second period x 12 = cranking speed of 192 RPM during the compression test (give or take 12 RPMs.)
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Regarding wet compression test - no bentley does not state you can't do it. In fact, it explicitely states you can. According to my bentley (covering '77-'84 Rabbit / Jetta Diesel) it states: "To determine whether the piston rings are causing low compression squirt a small quantity of SAE 40 oil into the low-reading cylinder(s) through the injector hole(s), and repeat the compression test. ..."
WOW!!! I just checked my Bentley manuals, and Jake is correct that the text he quotes is in the A1 Diesel Bentley.
The A2 Bentley has different text. It says, "Caution----Do not attempt a wet compression test on a diesel engine. The oil in the cylinder may be ignited by the compression pressure."
Both manuals are correct. If compression is low, putting motor oil (AKA fuel) in the cylinder and running another test will tell you if it's the rings or the valves. But if you get enough compression, the motor oil (AKA fuel) will ignite and your compression tester can explode. It's not too likely with a VW because the cylinder displacements are low and the volume in the guage hoses and the guage itself reduces the total compression pressure on the first couple of strokes.
Still, I wouldn't ever try a "wet" compression test on any diesel. I got out my red pen and wrote "Never do this" in my A1 Bentley where that "wet" compression test is described.
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Mark the Miser - on a leakdown test, to rule out the rings, engine oil is added. But unlike the compression test, the pistons are not moving up and down, it's just the rate of air leakage that is being measured, so the oil would definitely stay down around the rings where gravity would make it go. It would only help seal the rings. It would not get splashed around inside the combustion chamber by moving pistons and could not possibly help seal valves. It would indeed be more definitive test than a "wet compression" test.
I am thinking that based on my compression test, I've got some problem that's definitely not starter, electric, or fuel injection related. I'm thinking about the only thing I might think about doing is double-checking the cam timing before taking the head off. Although the evidence that I do have seems to be pointing to rings. I have not had bad sealing valves before so I don't know if they would be even or not. Keep in mind this is a freshly rebuilt head. Common sense says if the machinist screwed up the valve job, it wouldn't be exactly even on all cylinders. But at the same time, it is possible...
So anyway, I'm thinking next steps I should do are first double check cam timing, since it is easy to check. And then, I'm not sure... I'm debating between checking / changing valve clearances, or just taking the plunge and pulling the head off for testing.
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Racer-X (and others) That is interesting the A2 Diesel Bentley advises against wet compression test where other sources advise it. Is the A2 Bentley manual an official Volkswagen of America service manual? FWIW, the A1 Bentley is not an official VWoA service manual, and I know of several errors, and in general although better than most manuals, it is not the "end all" of reference literature.
The Diesel Protraining reference however is an official VW of America publication, and I trust it highest. It's the stuff that the dealerships got and used, and what Bentley lifted pictures and procedures out of when putting together their non-official manuals.
I don't think there are any problems with the wet test, as long as the glow plugs are disabled, and that the quantity of oil metered into the combustion chamber is 1 tablespoon, as recommended in the ProTraining manual. I am not sure of how effective of a test it is though. (I might find out if it is conclusive, as I keep diagnosing my engine problem.)
Another "tip" when compression testing I learned the hard way (it's not mentioned in any manuals) is that after you remove all your injectors for the compression test, be sure to move the "cap" from the fuel injector return fitting onto the injection pump's fuel return nipple. This prevents diesel froom oozing out and leaking down the front of your engine when cranking the engine for the compression test. :o
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Mark the Miser - on a leakdown test, to rule out the rings, engine oil is added. But unlike the compression test, the pistons are not moving up and down, it's just the rate of air leakage that is being measured, so the oil would definitely stay down around the rings where gravity would make it go. It would only help seal the rings. It would not get splashed around inside the combustion chamber by moving pistons and could not possibly help seal valves. It would indeed be more definitive test than a "wet compression" test.
:twisted: Thats not to say that the air would not also show up poor valve seating at the same time(hissing in inlet or exhust at TDC compression (stroke) :twisted:
I am thinking that based on my compression test, I've got some problem that's definitely not starter, electric, or fuel injection related.
:?: Two points here are causing conflict with my (sometimes)logical thinking..
Earlier on you mentioned observed change in cranking speed with 'three injectors out and four in...Is this right? I'd expect a doubling of cranking speed [ish] although your 190rpm sounds reasonable in itself [3 rev per sec]
The second point is your reference to 'fuelling must be good' WHY?
I'd loosen one injector line and under end of line do a fuel collection for a few cranks (GP's off) :?:
Common sense says if the machinist screwed up the valve job, it wouldn't be exactly even on all cylinders. But at the same time, it is possible...
:wink: Ah do you put all your money on a single number in roulette? :D
Mark-The-Miser-UK
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Mark - in theory, you do a leakdown first without oil added, this tells you the overall health of the ability of the cylinder to seal. Then you add oil and do the leak down again, and the difference tells you how much air was leaking past the rings. If the problem were with valves, I'd have to remove the head anyway to have the valve sealing problem fixed.
Re: cranking RPM with and without compression... Keep in mind that the energy used to push the piston up against compression during the compression stroke is energy that is returned to the crankshaft during the power stroke - assuming there were no blowby at all and also no loss of energy from compression heat conducted away. So the corrolary is that if energy loss from heat conduction was negligible and the cylinder was sealing pretty well, then we shouldn't expect a big change in cranking RPM by relieving compression in 1 or more cylinders.
Why have I ruled out fuel injection as a cause of the low compression: fuel injection and injection timing is not a factor used during the compression test, but yet the dry compression results, at 300-320, came out much lower than they should have been (400-500). I also know thereis fuel getting to the injectors when cranking (as it occasionally sputters and there is a smell of diesel and occasional smoke puff out the exhaust), and the car runs like timing is set right and everything else is fine when it is warmed up and idling and running.
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Racer-X (and others) That is interesting the A2 Diesel Bentley advises against wet compression test where other sources advise it. Is the A2 Bentley manual an official Volkswagen of America service manual? FWIW, the A1 Bentley is not an official VWoA service manual, and I know of several errors, and in general although better than most manuals, it is not the "end all" of reference literature.
Yeah, I think the A2 Bentley is in the same "official status" as the A1 Bentley. Technically it's an "aftermarket manual," but it was produced with assistance from VW and uses many pictures and borrows a lot of information directly from the official VW service manuals.
But I also think that the paperwork that came with my diesel compression guage had some very dire warnings about "wet" compression tests. Somthing like, "Never put oil or fuel in the cylinders when performing a compression test with this guage. The warranty doesn't cover damage from 'wet' comperssion tests and if you are injured or killed, don't blame us and be sure your heirs know that it's not our fault if you screw up that way." I might not have the language exactly right, but I'm paraphrasing it pretty close.
And other diesel engines I've worked on have warnings similar to the one in the A2 Bentley about "wet" compression tests.
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I asked an owner of the factory bentley about this and he posted the compression test page for me. It is inconclusive as it doesn't say to put oil in and it doesn't say not to either. Check the very last picture.
http://www.cardomain.com/memberpage/471729/8
Steve
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hey,
i've heard that because oil can't be compressed, if you do a wet test on a high compression diesel it can pressurize the cylinder and actually push the tester out with a huge force. im not sure that that could even happen with using just the force of the starter motor...but thats what i heard somewhere anyway.
good luck
Mark
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oil can be compressed a bit can't it??? :? I know water can't though.
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No liquid can be compressed as I understand it.
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One other thing to keep in mind, on a diesel, 1 Tablespoon is more than 80% of the volume above the piston at TDC. On a VW gasser, it's closer to 25-30% of the volume, and in larger gas engines, it's even less of a percentage of the compressed volume. So the increase in compression from the added non-compressible fluid in the cylinder is much less in a lower compression gas engine.
If all that oil stays above the piston, in a diesel, it could multiply the compression pressure by a factor of as much as 5 or 6.
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Well anyway- why in the world would his compression be consistently low across all four cylinders? I've seen quite a few compression tests, and even on a Chevy 350 with a zillion miles, the cylinder pressure will fluctuate more than that. And if there is a bad cylinder, the pressure will be a good bit lower. Just doesnt make sense that his readings are nearly exact in all four cylinders.....
Out of curiosity, did you use a thicker head gasket when you put the new head on? I'd be about 90% sure that there is nothing wrong with the valves sealing... even if there were, the compression readings would not be THAT consistent..
Somthin just aint stirring the Kool-Aid here.... ;)
Brendan
84 Scirocco 8v
00 Camaro L36 M49
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Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size. Searching for the conversion of 1 Tablespoon to cc, I found a few different conversion rates on the internet, clustered aroundd 1 Tablespoon = 15 cc. Let's use the precise rate I found of 1T = 14.786cc. In that case, 1 Tablespoon is about 88% of the combustion chamber size! I agree with you guys that this wet test is fishy. Filling the combustion chamber with 88% liquid implys that it is expected to see a significant increase in compression numbers during the wet test, regardless of the condition of the rings. Looks like I shouldn't be too quick to condemn the rings.
Brendan, I also am kinda baffled as to what could explain the even lowness of the dry compression results. I used the thinnest, 1-notch head gasket, which was called for by piston projections. (The Piston projection numbers have been posted earlier in this thread.) It almost seems to imply... something is out of spec that is uniform to all cylinders... IE: cam timing or valve clearances. I did have the intake valve clearances set on the tight end of the specs... I could try changing that to the middle of the specs (cost of 4 adjustment shims is not bad...) and see if it makes a difference. I could also re-check my cam timing while I'm under the valve cover. It could be worth a shot, to try and rule valve timing out.
I could also consider getting the car back ready to drive, jump starting my motor (which is a lot easier with the rebuilt starter! :D ), and driving it somewhere to get a leakdown test, to try and conclusively detect whether the rings are bad. Thanks for helping me work through this guys!
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Re: cranking RPM with and without compression... Keep in mind that the energy used to push the piston up against compression during the compression stroke is energy that is returned to the crankshaft during the power stroke - assuming there were no blowby at all and also no loss of energy from compression heat conducted away. So the corrolary is that if energy loss from heat conduction was negligible and the cylinder was sealing pretty well, then we shouldn't expect a big change in cranking RPM by relieving compression in 1 or more cylinders.
Ah yes there is energy input from the compressed cylinder air...
But this only reduces the energy required. This is why a cranked engine goes wah wah wah wah where it speeds up and slows down (4 times a revolution) I have not done a comparison with my diesel but if you can compare cranking with sudden turn off of fuel solenoid with the key; the engine rotation doesnt peeter away but stops within a rev(ish) I guess the larger the flywheel the more even the cranking speed for any particular cranking speed. Many times I have done this on gassers...Including last week when I jump started my 1970 Bedford with 15ft cables (couldnt get my Quantum closer) There was no battery on the Bedford ; it had been stood since last August and last filled with petroleum in the previous September (2003). Cranking speed soon dropped down even with my 'Q' fast idling. I remembered my old trick and removed two spark plugs. Cranking speed felt like it doubled and the old girl fired up..
Why have I ruled out fuel injection as a cause of the low compression: fuel injection and injection timing is not a factor used during the compression test, but yet the dry compression results, at 300-320, came out much lower than they should have been (400-500). I also know thereis fuel getting to the injectors when cranking (as it occasionally sputters and there is a smell of diesel and occasional smoke puff out the exhaust), and the car runs like timing is set right and everything else is fine when it is warmed up and idling and running.
Sorry Jake I was thinking of the link of poor starting fuel supply to poor starting; and not as the cause of poor compression... with fuel ratios at idle alledgedly only requiring nearly 200:1 this may be too weak for starting hence a cranking fuel volume check might show something.
:twisted: Remember all we want to achieve here is to cure your hard starting so my occasional lateral interject is only an attempt to solve a mystery assuming its not simply a ring thing :twisted:
:idea: Yes or no on the wet compression test?... I say yes! Chances of igniting a drop of oil in a cold engine that is hard to start with a spray of fuel and glow is um er ziltch :wink:
Worried about using up over 50% of compression chamber? Then use a gauge with a reservoir of air between the two valves on the ends of the gauge hose. (a fatter or longer pipe with a teaspoon of extra capacity would do) :idea:
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Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size.
Well, if you want to be precise, it's 1588cc / 4 cylinder / (23 - 1) = 18cc in the combustion chamber.
There's 396cc of displacement in the cylinder and 18cc above the piston. So compression is ( 396 + 18 ) : 18 = 414 : 18 = 23:1.
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Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size.
Well, if you want to be precise, it's 1588cc / 4 cylinder / (23 - 1) = 18cc in the combustion chamber.
There's 396cc of displacement in the cylinder and 18cc above the piston. So compression is (396+18) : 18 = 414 : 18 = 23:1.
:shock: Yep your math is correct although not easy for the non mathematical to follow due to lack of steps and strictly speaking a shortage of parentheses (brackets)... I assume that the Bentley is referring to the American tablespoon which is a pesky 2/3 of our Limey one and so about 9cc. or 50% of the chamber size. Why not use one of your puny teaspoons or about 3cc. 8)
:twisted: If this wet test is going to work properly we need to drive the car half onto the side walk inorder to be sure of spreading the oil over the entire compression ring including the gap! else oil is all in a 'corner':twisted:
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:lol: :lol: :lol: this place is great for a good laugh sometimes
Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size.
Well, if you want to be precise, it's 1588cc / 4 cylinder / (23 - 1) = 18cc in the combustion chamber.
There's 396cc of displacement in the cylinder and 18cc above the piston. So compression is (396+18) : 18 = 414 : 18 = 23:1.
:shock: Yep your math is correct although not easy for the non mathematical to follow due to lack of steps and strictly speaking a shortage of parentheses (brackets)... I assume that the Bentley is referring to the American tablespoon which is a pesky 2/3 of our Limey one and so about 9cc. or 50% of the chamber size. Why not use one of your puny teaspoons or about 3cc. 8)
:twisted: If this wet test is going to work properly we n
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I checked a few things out with my GTD motor the other day. It looks like the engine builder set up a couple of the intake valves and one exhaust valve (checked on a cold engine, at least) too tight, so I installed slightly thinner shims bringing them all into specs (although generally towards the tight end of the specs.)
I also found that the cam timing was off a little bit. The cam was retarded a bit (I figure by about 2 degrees, since I measured it being off at the flywheel TDC reference by about 4mm, which I'd estimate sits at about a 9" diameter. You can do the math.) I think this was off because previously I didn't leave the cam locked when tightening the cam pulley bolt like is required to prevent things from moving when tightening the bolt. So I re-timed the cam, following the bentley procedure of leaving the cam locked when tightening the cam pulley bolt this time. (We should try and remember: lock cam when tightening the pulley bolt, unlock cam when loosening pulley bolt).
In theory, the earlier-closing intake valves should help build low-RPM compression. It should be interesting to see if what I did makes any noticeable difference.
I cranked the engine over some to prime the high pressure fuel lines and clear some oil out of the combustion chambers from the wet test, although wasn't able to start it, I'm hoping just because the battery was down (have I mentioned this is a really small battery, and I don't think I charged it since doing the wet compression test.) So I set the battery on a trickle-charger, and that be ready to make a run at starting the motor next time I get to working on the car. I hope it works!
PS - good catch, Racer_x, on the combustion chamber volume calculation error.
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Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size.
Well, if you want to be precise, it's 1588cc / 4 cylinder / (23 - 1) = 18cc in the combustion chamber.
There's 396cc of displacement in the cylinder and 18cc above the piston. So compression is (396+18) : 18 = 414 : 18 = 23:1.
:shock: Yep your math is correct although not easy for the non mathematical to follow due to lack of steps and strictly speaking a shortage of parentheses (brackets)... I assume that the Bentley is referring to the American tablespoon which is a pesky 2/3 of our Limey one and so about 9cc. or 50% of the chamber size. Why not use one of your puny teaspoons or about 3cc. 8)
:twisted: If this wet test is going to work properly we need to drive the car half onto the side walk inorder to be sure of spreading the oil over the entire compression ring including the gap! else oil is all in a 'corner':twisted:
Puny? Hah! :D ;)
Actually, our respective volumetric measurements have a close and intertwined history.
Back in the 18th century there were two gallons in common use in both Britain and North America...the wine and the imperial gallon. The wine gallon was based on a 7" wide by 6" tall cylinder and was the basis of taxation (smaller gallons made for more tax revenues...), while the imperial version was based on 10 pounds of water (a wine gallon weighs about 8.33 lbs).
When the USA went their own way from Britain public sentiment was pretty much against anything with the "imperial" ring to it, so the fledgling government chose the wine gallon as a standard measure of volume. Later it was formalized to exactly 231 cubic inches. (A cylinder 7" wide and 6" tall is 3.5^2 x 3.14159 x 6 = 230.9 cubic inches.)
In any case, the wine gallon was always volume-based and fractionally divided (the imperial gallon was weight based). A gallon has 4 quarts, each of which has 4 cups of 16 tablespoons (a 4th of a 4th).
Pretty cool, eh? ;)
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Racer_x is right about 1 Tablespoon being a large quantity of our IDI VW Diesels' combustion chambers. I did a calculation of the combustion chamber size to verify this. 1600cc / 4 cyl / (23 + 1) = 16.66 cc combustion chamber size.
Well, if you want to be precise, it's 1588cc / 4 cylinder / (23 - 1) = 18cc in the combustion chamber.
There's 396cc of displacement in the cylinder and 18cc above the piston. So compression is (396+18) : 18 = 414 : 18 = 23:1.
:shock: Yep your math is correct although not easy for the non mathematical to follow due to lack of steps and strictly speaking a shortage of parentheses (brackets)... I assume that the Bentley is referring to the American tablespoon which is a pesky 2/3 of our Limey one and so about 9cc. or 50% of the chamber size. Why not use one of your puny teaspoons or about 3cc. 8)
:twisted: If this wet test is going to work properly we need to drive the car half onto the side walk inorder to be sure of spreading the oil over the entire compression ring including the gap! else oil is all in a 'corner':twisted:
Puny? Hah! :D ;)
Actually, our respective volumetric measurements have a close and intertwined history.
Back in the 18th century there were two gallons in common use in both Britain and North America...the wine and the imperial gallon. The wine gallon was based on a 7" wide by 6" tall cylinder and was the basis of taxation (smaller gallons made for more tax revenues...), while the imperial version was based on 10 pounds of water (a wine gallon weighs about 8.33 lbs).
When the USA went their own way from Britain public sentiment was pretty much against anything with the "imperial" ring to it, so the fledgling government chose the wine gallon as a standard measure of volume. Later it was formalized to exactly 231 cubic inches. (A cylinder 7" wide and 6" tall is 3.5^2 x 3.14159 x 6 = 230.9 cubic inches.)
In any case, the wine gallon was always volume-based and fractionally divided (the imperial gallon was weight based). A gallon has 4 quarts, each of which has 4 cups of 16 tablespoons (a 4th of a 4th).
Pretty cool, eh? ;)
So what youre saying is yours is smaller than mine :shock:
I feel I'm chasing you around the threads (I've shown you mine why won't you show me yours 'Quantum mileage' that is :wink: )You can quote it in wine gallons if you like :twisted:
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I I think this was off because previously I didn't leave the cam locked when tightening the cam pulley bolt like is required to prevent things from moving when tightening the bolt. So I re-timed the cam, following the bentley procedure of leaving the cam locked when tightening the cam pulley bolt this time. (We should try and remember: lock cam when tightening the pulley bolt, unlock cam when loosening pulley bolt).
.
:idea: When I replace the cam sprocket I always clean the taper and then use a little abrasive kitchen cleaner to give a good non slip interference fit (Add creme and 'lap in' with sprocket. Remove wipe clean and replace. Reduces fear of sprocket slippage. Seeing some geezers have snapped their timing slots; I'd only 'nip up' with timing bar and then complete using a pair of grips holding between lobes. :idea:
Rip me t oshreds if you wish; its just my personal method and I've never bent a valve :twisted:
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I've got a GTD autocrosser update!
For the first time in months, I put a little attention to my Rabbit GTD 1.6lTD autocrosser. You guys might recall last time I worked on it (look up four posts in this thread), I reset the cam timing and adjusted a couple valve shims to make them less tight. That was after I had fixed an excess voltage drop problem across the starter solenoid (which boosted cranking rpms... although still not enough to be able for a boosterless cold start), and after that, checked the compression to find peak cranking pressures were low, although even. Busy finishing off a master's degree, I have just let the project sit under the car cover since then.
Now, feeling good following the success of VNT-turbo'ing dad's Rabbit 1.6, I decided why not take the car cover off my Rabbit and see if she might actually start? I didn't try recharging the battery (which is a miniature, lightweight racing style), but found it checked out at a touch over 12.5 volts - seemed OK. I got in the car and gave it a good full glow plug cycle as I usually do for hard starting motors. I recalled waiting for the glow plugs to switch off let the engine crank over a little quicker, so that was my strategy. I had also since the over-revv incident, installed a slow glow relay into this car, but man does it seem to take a long while until I actually heard it click off... over 40 seconds I'd say and it's not like it's that cold out. I was imaging my battery draining and draining...
As soon as I heard the glow plug relay click and shut off current to the glow plugs, I started cranking. It cranked quite brisky, feeling as if it might start, although after a few seconds it still hadn't reached RPMs with were self-sustaining. The RPMs were starting to drop now, for sure the battery voltage was dropping. I stopped cranking,and felt my heart sink a bit. Decided to make one last attempt at starting the motor on this several-month old battery charge... I gave it a little bit of glow plug, just a few seconds this time - perhaps just long enough to make the light go out - and with glow plugs still blazing, switched on the starter. It cranked over, yes, a little bit more briskly now... quickly increasing in speed quick enough, and yay - was running all by itself! :o I started the thing without even recharging the battery after letting it sit for months! :D
Driving it was like being reunited with a good friend. I enjoyed being reacquainted with it's characteristic mufflerless motor roar and turbine whine. This thing is such a high performance machine... especially after getting used to driving dad's daily driver Rabbit (which has bilstein HDs, stock GTI springs and swaybars) the GTD autocrosser just handles like crazy, despite decades-old, bald tires; one of them even showing some cord! (I know I need to do something about the street tire situation.) Engine still pulls like crazy, just as long as I don't lug it so much as to keep the turbo working. But with some shifting attention, the close-ratio five speed allows that, and the peloquin torque sensing diff puts the power down nicely. With the copious fueling quantities, even off-boost it gets decent acceleration. And it's just pretty crazy with the foot in the floor when the boost comes on! :)
And I became reminded there are still many old problems I've got to fix before I can start racing it again... there is a clunking/knocking I can feel through the pedals/floor when the clutch is engaged. The fuel injection still needs some fine-tuning to make it easier to control the throttle - sometimes the RPMs don't want to return back down at all. There is a bit of oil coming out of the blowby vapors I need to deal with and make it clean, even if it means installing a bulky and pricey MANN pro-vent. The clutch pedal needs adjusting. And I previously took the carpet out to clean, which I need to re-install along with all the trim that goes over the carpet. But anyway, I was thrilled to have started it up on the first try (ok maybe second try.)
Just wanted to let you guys know... I think the cam timing and/or loosening up the intake valve clearances made a difference with making the engine easier to start! VW powertrain engineers knew what they were doing when they designed the intake valve to close as early as it does.
I can't help think there was something that happened to the motor either during those brief few seconds when it was over-revving, or after when I was putting the head back on, that reduced it's low-speed compression. High-speed compression, FWIW, seems great to me, at least if engine power is any incication. I remember when I had the head off and was prepping for reinstalling the new one, cleaning off all the carbon deposits from around the tops of the cylinders... maybe I shouldn't have done that? I remember taking the scotch-brite pad into the area where the top ring sealed, although I tried moving the pad in the same direction as the hone marks and also thinking the scuffing was only very light. I also remember thinking that the bores looked as good as I could imagine they could, at least by my untrained naked eye. I am wondering if I should try putting some non-synthetic oil in the sump and taking it for a long hard drive, to see if I might be able to get the top compression ring to reseal.
Anyway, even if I can't make it any easier starting, I can probably use it "as-is" for another racing season or two. I could lug around one of those big 40-lb optima batteries with me in the trunk to events and use it if the standard battery can't get the cold starting job done. Maybe I could mount it to a little cart and hook up some big booster battery cables with a quick-release connection engaging to the main starter cables for some starting voltage assist. But of course, if it's possible to cheaply do, I would love to try and raise the compression back up and make the engine start as easily as it used to. Actually if I could get the engine compression as good as it used to be, it should not start better than it used to with the voltage drop in the starter solenoid fixed.
I am looking forward to getting this car prepped for racing again and taking it out to the local events... I haven't even raced on my new custom CNC-machined / lightened racing wheel centers yet!
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hey jake, check out www.oilextreme.com
the idea is there, and if it works like they say it does, then that is the oil you need to win :twisted:
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That was a very interesting read, I still look forward to your progress :) Your VNT thread had me thinking of trying one in the near future for my 1.6TD.
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Nice update, Jake... I know what you mean about feeling "reunited" with an old friend when you drive your racer again. I brought my FSP car out the other day and remembered why I built the car in the first place.
Got any pics to show of those snazzy new wheel centers?
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veeman - I don't have any pics of the wheels installed on the car, but here is a pic showing the lightened wheels with race tires mounted:
(http://www.imagestation.com/picture/sraid129/p4ab384dce3b5b9b93a3473450d19cfbd/f7cc1aab.jpg)
Since that shot was taken, I had the wheel centers anodized black:
(http://www.imagestation.com/picture/sraid149/pfec1aa733282dc9a0c4a56f86b911d8f/f5fa2af3.jpg)
jtanguay - I don't think any kind of low-friction oil would be the hot ticket for getting rings to re-seal. As for the claims of that dino oil being better than a quality synthetic, that oil has been out for a while now but I have yet to hear a positive recommendation coming from an unbiased source.
I knew another racer years ago who was using (and peddling) that recycled dino oil. When he pitched me on it he lost me after the part about "reprocessed and recycled dino oil" (I also had in the back of my mind knowledge that he stood to profit from selling it.) It also didn't sound like he had tested it against a high-quality synthetic.
He was racing a pretty seriously prepared diesel though! He had a very nice gray turbodiesel mercedes sedan that he gutted and installed a roll cage into as well as all the other necessary safety gear for high speed time trials / lapping days. He had r-compound tires too IIRC, and some healthy engine mods including extra fueling, boost, and a very well-installed intercooler. I remember the body and paint (metalliic silver in color) were flawless and the car was clean. It was pretty fun to see another guy out having fun racing a diesel.
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I feel I'm chasing you around the threads (I've shown you mine why won't you show me yours 'Quantum mileage' that is :wink: )You can quote it in wine gallons if you like :twisted:
Sorry I missed this, Mark. I am currently averaging in the low 40's/US gal in local driving on a mix of rural roads and city driving...no motorway. :D
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I feel I'm chasing you around the threads (I've shown you mine why won't you show me yours 'Quantum mileage' that is :wink: )You can quote it in wine gallons if you like :twisted:
Sorry I missed this, Mark. I am currently averaging in the low 40's/US gal in local driving on a mix of rural roads and city driving...no motorway. :D
Blimey I've grown a beard and bought a third diesel Quantum since this posting. My current 'Q' will come off the road at the end of September for a 'scale and polish' It's doing about 40 US mpg (mainly town) at the moment. My replacement although 2 years older has only done 105000 miles. Running next to each other I can tell this new old one has a quieter engine all round. Even the turbo is ultra quiet. My usual runner has a kind of 'fishtail' warble to it which I'll miss. Funny how the turbos sound different. One I listened to on the first TD Quantum I ever sat in was so high pitched that it was uncomfortable to drive with the windows down. .. Seller claimed this was normal. That experience very nearly stopped me considering TDs... Luckily I tried one more!
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Jake,
Were you running any kind of short-shift and/or weighted shift kit when you over-revved?
Curious,
-Josh
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Yep, various pieces, some custom, some readily aftermarket available, including techtonics short shifter set at 30% and some missing linkz pieces.
The part that increased friction side to side of my linkage drastically and I believe contributed to the missed shift was the missing linkz relay shaft shim:
(http://www.4crawler.com/Diesel/ForSale/Images/shiftkit_41t.jpg)
It felt great when I installed it initially, as I left the bolt not fully tightened to keep it from binding. This was a big mistake! As I used the shift linakge more, and the racing practice day progressed, the relay shaft bellcrank bolt tightened on itself, and it progressively bound up my shift linkage in the side to side direction of movement.
It turns out the way Roger recommends installing this shim is to file/sand down the bushing so the bolt can be tightened fully without there being friction. I have since had a word with Roger Brown about the importance of including installation instructions in hardcopy with his kits. He has since then improved his online instructions, clarifying/emphasizing the correct installation instructions for this piece.
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I pulled the pan and inspected the bottom end situation on my Rabbit autocrosser yesterday. Everything checked out A-OK: thrust clearance (.006"), rod to crank axial clearance (.006-.009"), rod bearing to crank clearance (.0015-.002"), and main bearing clearance (.0015 to .002").
As I dreaded, I found that this motor has the one-piece integrated thrust/main bearing... although this one seems to be holding up well!
(http://www.imagestation.com/picture/sraid184/ped39582ee6568e2faa4592c0b8773c47/f28af82b.jpg)
It is interesting to note that this thrust bearing has a copper layer inside, which wasn't present in the failed one-piece integrated thrust/main out of dad's Rabbit 1.6lVNTD. They were apparently made by different manufacturers.
Some of the mains and rod bearings had some of their outer layers worn through in spots. I took a couple mains down to my machinist/vw engine dude for inspection, and to get his advice. He noted that in one spot of the 3rd main that he said you could tell it was just getting down to the copper layer. But he said it should be fine to just run with both the old main and rod bearings given the good plastigage clearance readings. Do you guys agree that these bearings should be OK to run?
3rd main:
(http://www.imagestation.com/picture/sraid184/p7ebfad14626a407b96cc537b58bef979/f28af71e.jpg)
4th main (which was the gasser type :? ):
(http://www.imagestation.com/picture/sraid184/p407ce89c0061b442bfb090577df8b1d6/f28af5db.jpg)
Some pictures of the rod bearings:
#1
(http://www.imagestation.com/picture/sraid184/p6754503f558eadbbcf8a25a23d81fb54/f28aefb1.jpg)
#2
(http://www.imagestation.com/picture/sraid184/p9783df3a47ccf83bf42c8c798e91c297/f28af10e.jpg)
#3
(http://www.imagestation.com/picture/sraid184/pbb30e852528071851a2927518331d7b8/f28af069.jpg)
#4
(http://www.imagestation.com/picture/sraid184/pcb433832b1832d2029c299b4b6f04fcd/f28aef02.jpg)
I found blueing on one part of the crankshaft, but thought it was odd when I dug in to find all the wearing surfaces looked fine. My VW engine guy said he often finds this on VW crankshafts, and believes it is heat from the crank manufacturing process, not necessarily from from engine operation.
(http://www.imagestation.com/picture/sraid184/p7cd30e1230055d218dd41801d9df289a/f28af33b.jpg)
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Jake
Just put in a new set of rod bearings and run it.
Looks like checking crank end-play is going to be part of my oil change routine.
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For 50 bucks I would just change the bearings, its cheap insurance. Not sure what throw of the crank is pictured but the #4 crank throw has its radius induction hardened, that would explain the bluing.
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Jake,
I have to agree, slap in new bearings. Something to note when installing the thrust/main bearings; it is advisable to place a bit of a load in the direction of clutch release (axially, towards cylinder #1) before fully tightening the main cap which houses the thrust main bearing. Sometimes, the uneven wear characteristics of the upper and lower bearing shells are directly related to not performing this "thrust/main bearing" setting operation.
Incidentally, where is the best place these days to get bearings, both mains and rods?
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QuickTD: the blueing on the crank was next to the #2 rod journal.
Also, I found this old post of yours where you replaced some rod bearings that were giving you trouble in your 1.9: http://www.vwdiesel.net/phpBB/viewtopic.php?t=69
I was wondering if you recall if you plastigaged those rod bearings before you replaced them, and if so do you remember if their clearances were in spec?
2383 - Thanks for the tip on installing the integrated thrust/main#3 bearing. I've heard the same tip from other very credible sources, so there must be something to it.
I would love to go ahead and replace all my rod and main bearings, new rod bolts, etc, but unfortunately right now I am pretty limited on budget. I also need to consider that this motor might not have the best ring seal due to the hard cold starting problems last winter and spring. I am still mulling over what to do...
My rod bearings clearances (according to the plastigage test) were specifically: #1: .002", #2: .002", #3: .0015", #4: .0015". All those are not only under the wear limit for old bearings (< .047") but is still within the specs for new bearings (.0011-.0035").
I would love to be able to try revving this motor out above 6kRPM and not have it break...
The rod nuts get toqued to 35 ft-lbs by the way, according to Bentley (IIRC), so supposedly they are re-usable, although I found on mine that the threads in the rod nuts were beginning to extrude out, which I don't like, so I think I'll at least replace my rod nuts with new geunine VW ones (at only a couple bucks a piece.)
Does anyone know how much tensile strength the stock rod bolts/nuts are rated at? Are they the standard grade 12.8 / 176kpsi?
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Well, I decided I didn't like the way the upper rod bearings looked too much, so I just ordered a set of new rod bearings. You'd never guess who had the best price on them, at only $14 a set. The VW dealer! :lol:
Also for a little added peace of mind at high RPMs, I am also going to throw on a set of new genuine VW 9mmx1.0mm shouldered rod nuts. They also wearen't too bad in price... $1.82 a piece from the dealer (or about $15 for a set of 8.)
2383: As for where to get bearings from, check out this thread: http://www.vwdiesel.net/phpBB/viewtopic.php?t=1908
I'd recommend using the thrust washers rather than the integrated main/thrust. You'd (obviously) need a couple extra main and crank bearings for your 6-cylinder motor.
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My parts arrived and it turns out what I thought was a "set" of connecting rod bearing shells from the VW Dealer is really just one shell! (IE: not even enough to do one cylinder!) :( Needless to say, I sent that $15 bearing shell right back to "the Stealer". Guess I'll just be reusing my old bearings for now. At least they're tight!
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Kolbenschmidt OEM rod bearings are only $30CDN for a set of 8, mains are $50CDN for all 10, thrust washers are $12CDN for all 4 at any aftermarket parts supplier. I would not suggest the dealer for bearings unless you wan't to dispose of a bunch of money.
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I did a leak down test on my GTD autocrosser on cylinder number four with my new homemade leakdown tester.
Result: 26% leakdown at 100 psi :shock:
Almost all the leakage seemed to be coming out through the rings. I had the oil pan off and it was really easy to tell that was where all that rushing air noise was coming from. There was very little noise and no noticeable flow through the air intake or exhaust.
I tried filling the cylinder with oil and re-testing, but the oil kept getting blown through. It only held pressure (when it seemed really quiet) for about one second and I wasn't able to see what the % leakdown was. But right after the oil got blown through I think I saw 4-6%, dropping to 10% and below.
Looks like it's time for some new rings at least. I'm just amazed how well the motor pulled considering its 26% leakdown!
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Update: the head's off, and the pistons are out!
I found the rings have what seems to be excessive ring to piston groove clearance. Bentley says upper end of the range should be .002", but on the one top compression ring I measured, I found .006"-.007"! Could that be the culprit for the low compression and high leakdown?
Any of you guys with experience re-using pistons with new rings check your ring to piston-groove clearance, and what did you find?
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Update: I had the pistons bead blasted to have them cleaned up, and have a set of new rings here ready to install. With the new rings and bead blasted ring lands, the ring to ring land clearance tightened up to like new specs (.003" on all the compression rings). :)
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Any pics of the final product? I have a bead blaster and would be interested in trying that. Any idea what size of glass shot was used? thanks jake
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I'll take some pics for you. :)
My engine builder did the piston prep... I'll ask him what size glass beads he used.
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Pics for Dave of the bead blasted pistons:
(http://www.imagestation.com/picture/sraid192/pebfa2ac0a19d194eca04d3d37824d523/f1b625b3.jpg)
(http://www.imagestation.com/picture/sraid192/pf059cfef642962bda75fb991c6f7d401/f1b62553.jpg)
(http://www.imagestation.com/picture/sraid192/p4ad9af00a3bf7b486ee5b80227630394/f1b624d4.jpg)
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Very nice! What are the ridges near the top edge of the piston? I don't think I've seen those on gasser pistons... Something to do with the thermal expansion abilities of the TD piston perhaps?
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Holy moly! Those were used pistons??? Good lord, they are beautiful!
I've seen new pistons that didnt look that good... ;)
NICE! :)
Brendan
84 Scirocco 8v
00 Camaro L36 M49
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I am gonna take a wild guess and say that is likely #8 glass shot. I assume you are coating the pistons? If so with what, and do you have any measurements of the diameter before and after the blasting. Bead blasting could be a good thing for these pistons as it hardens them much liek shot peening. I have see tests comparing hardening between both lead and asteel and glass shot and there was hardly any difference between the steel and glass. I'll see if I can find that info again.
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I am pretty pleased with how they turned out. The service actually wasn't very expensive. I've heard if you do this, that it's important to clean out all the old glass beads from the grooves before installing the rings.
Dave - I didn't know bead blasting gave similar results to shot peening, that is pretty cool! I do understand it roughens the surface, allowing more places for oil to hang out at, which can't be a bad thing for skirt lubrication.
I won't be having these pistons coated, because that kind of investment just doesn't make sense on these used pistons. These ones have actually been smacked into valves on two different occasions! (This is very apparent in their crowns... which you can check out pics of in page two of this thread.) My main goal with this engine work is just to get the car back "ready to race" reliably (with ring leakage issue addressed), and within my current budget. It's going to be good to have the GTD up and running again. :P
Veeman - according to this online Car Craft article, (http://www.carcraft.com/techarticles/77899/,) "anti-detonation grooves above the top ring land are said to knock the peaks off shock waves within the cylinder."
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What do your piston-rod assemblies feel like? Before I rebuilt my 1.6NA, it had, among other major problems (like colossal oil consumption and smoking), a little lower-end tap in it. All my rod and main bearings were in beautiful shape (this motor had a full rebuild only 90k ago; something must have been done to the rings--maybe overheating--to make them lose their tensile strength after that), so I was mystefied as to the possible source of this sound. Then, as I was reassembling it after honing and installing new rings, I noticed that the wrist pin one the #1 rod-piston assembly was a little loose. Not LOOSE, but not like the others. On the other three, the wristpin was fixed--pressed in--to the small end of the con-rod, and then floated free in the piston (held in by circlips at either end, one of which was also loose on #1). On my #1 assembly, the pin floated in both the connecting rod small end and in the piston. I figured this might be the source of the noise; I took the circlip out and bent it so that it fit tightly, and slapped it back together.
What do yours feel like? Are the wrist pins all fixed in the conrods and floating in the pistons? Mine was not loose like rattling loose, it was just able to move inside the conrod end. Also, what do you (all you guys) think could be the consequence of this? I reused the pistons, didn't have the block bored, and replaced no bearings, and I have a spare shortblock so if this goes it won't be a huge deal, just kind of a pain in the ass. But I'd like to make sure the head can't get damaged. I don't suppose it could throw a rod, per se, but I can imagine other bad things happening. The noise was gone for the first few hundred miles after the rebuild, but has now returned. I think maybe the piston pin circlip has come loose again--it was a non-stock clip, not like the others in the engine. If that came out, what would happen, do you think? Just score the hell out of my cylinder wall, I suppose...???
Thanks... :shock:
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On a 1.6lNA motor I recently re-ringed (the 1.6VNTD), I recall all of its wrist pins were a medium/light press-fit into the pistons. I'd describe it as just light enough that you can press the pin into the piston with your hands, no special tools required. Sliding the rod back and forth inside the piston, the rod slid across the pin before the pin slid in the piston. (I actually can't remember if the pin slid in the piston at all for the purposes of this test, it might have not.)
The 1.6lTD pistons seem to have a noticeably looser fit of the piston pins. I have read a reference that on the turbo pistons the pin piston to clearance was increased. Having recently handled both, I think I can verify this is true. The rod pushes in and moves around from side to side noticeably easier in the TD piston than it does with a NA piston. Sliding the rod back and forth inside the piston, the pin slides inside the piston before the rod slides over the pin.
The design of these pins is called full floating. The idea is with everything at operating temperature, the pins are supposed to be able to rotate around and distribute the wear and lubricating oil all around. They get their lubrication from a hole in top of the small end of the rod. What you describe "not rattling loose, but able to move" sounds right to me. The main advantage of them is that they are easy to disassemble and reassemble, as you don't need a press.
Be really careful removing wrist pin clips if you plan on re-using them... if you bend one and put it back in so it could come out while the engine was running, it seems like it would do some pretty serious piston wall damage. Next time you have a bottom end apart if you want extra peace of mind, install new pin retaining clips.
I'm sure new pin clips are cheap... let's see. Looks like the part number is N 012 277 1, known at the dealer parts depts as "lock ring" remarks "C24x1.5", 8 needed per motor. Yep, they retail for under 50 cents a piece.
I know certain types of applications that are pretty extreme (like baja style off-road racers constantly crashing over bumps) make improvements in the piston pin retension department, upgrading the clips to special one-use-only spiralox retainers (since they get destroyed every time you remove them, there is no temptation to re-used them like there is with c-clips).
You also sometimes hear about teflon buttons getting installed near the pin ends to minimize the damage "just in case".
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Update: I got the bores deglazed:
(http://www.imagestation.com/picture/sraid193/p81d9ed4c865118d9e9098f906c2f3cae/f19e0ca1.jpg)
There were some vertical scoring marks in the bores that woulnd't come out... hope these vertical marks are OK. If you look really close you can make some out in this close-up. They are hard to see in this pic, but if you shine the light on them just right they really stand out.
(http://www.imagestation.com/picture/sraid193/pd5cfcb1028af7031b0eb232651c77c48/f19c8463.jpg)
Besides those vertical score marks, the honing seemed to have cleaned up all the other blemishes in the walls quite well. I wonder how the vertical marks got there in the first place, and also if they are going to hurt the ring seal?
My rings are the "pre-gapped" variety. I measured my ring clearances near the top of the bores just below the ridge, where in theory the bores will be most worn so gaps should be the largest.
Here is how the ring gaps measured out in that location:
* Top compression rings: .022"-.024" (new specs: .012"-.020", wear limit: .039", according to bentley)
* 2nd compression rings: .017"-.021" (new specs: .012"-.020", wear limit: .039")
* Oil scraper rings: .014"-.015" (new specs: .010-.016, wear limit: .039")
So generally measured at that location, the gaps are generally right on the loose border line of the "new" specs.
It would be interesting to see how much tighter the ring gap gets if I set the ring down near the bottom of the cylinders where the bore should be tightest. Maybe I'll push one down there and see what happens. 8)
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looks good jake did you cover the crank and take out the oil squirter when you deglazed the block in car?..i've hit em trying that before and had to rebend them back to shape no fun.. the pistons you had beadblasted..you may want to watch that..i remeber in class they always taught us to beadblast ont the top of the piston..never the sides or the ring land..because the glass bead and get impregnated into the aluminum...then it comes outlater ..kinda like a sand or galss bead injection to your piston skirts ..but a good idea..i remember reaming ie crosshatching skirts to get them to fit tighter but that was temporary..as they raised portion would wear down after a while... Im surprised your machinist beadblasted the pistons for you ..blakes machine shop where he worked almost sh*t a brick when he mentioned it..and my machinist also said it will end up causing you problems later..
thanks...just a heads up
Deo
\x/ hillfolk!
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I would worry a bit about glass retained in the skirt as well. A good wash in hot soapy water will help get the grit out. We always washed honed blocks with soap and water and a plastic scrub brush, solvent will not remove the honing grit. After soap and water washing we rub down the bores with a white rag wetted with engine oil, keep rubbing until the rag comes out clean. It's surprising how much crud comes out.
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Thanks for the info guys... I read a bulletin by hastings (a ring maufacturer) warning about glass beads remaining in the ring lands, recommending to clean them out after bead blasting. The glass beads if left in the ring lands can abraid the ring land surface and the rings. The bulletin and other additional information are in these links:
http://www.hastingsmfg.com/Service%20Tips/enginering_bulletin_cleaning_pis.htm
http://www.hastingsmfg.com/Service%20Tips/pressure_cleaning_media_in_engin.htm
http://www.hastingsmfg.com/Service%20Tips/pressure_blast_cleaning_engine_p.htm
I wan planning on wiping/scouring the ring lands with brake cleaner and paper towels and maybe a brush to try and dislogde and flush away any glass beads that may be in there.
Deo - yes I removed my piston cooling oil jets... nearly had to remove the block and drop the crank after discovering a stripped oil jet screw, but I got the stripped bolt extracted successfully without having to drop the crank. :) Here is the related thread:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=2307
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My cylinders had those vertical streaks too after I honed them. I think it's no big deal. I couldn't feel them with a fingernail, so I figure they can't mean much. My car uses literally ZERO oil (like, not a single damn drop even during break-in), and has perfect compression and no smoke, so I have no complaints.
Thanks for the info about my con-rods and stuff. Man, do I ever feel like an idiot for not replacing that circlip. In fact, next time I think I might just replace all of them with new ones for good measure. I bent this replacement clip (which looked more like a cut-up key ring than a machine part like the rest of them) so that it fit in there very snug, but it was loose and rattling before, so maybe the heat got to it and it is back to jumping around in there. I'm not gonna think about it...I cannot afford to rip into that thing again for another few years. I can rarely hear it anyway, so I will just drive it till it blows then drop in a fully rebuilt one (I used sloppy old pistons and reused bearings on this one anyway).
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Here's what my bores looked like. Similar deal.
(http://memimage.cardomain.net/member_images/9/web/2049000-2049999/2049336_9_full.jpg)
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Heh. When I was in college I pieced together a 1.8 gasser from free, broken engines while I was working at a VW Porsche shop and going to school.
THere was one bore where the block I had gotten for free had lost a head gasket where you could feel a 1" wide section where the coolant had washed away the oil and the bore was more worn. The owner of the shop said not to worry about it for a decent motor.
The engine turned out great, and I used to beat up on my GTI driving buddies and it didn't noticeably use oil or make smoke.
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Just out of curiosity, were you at Colorado College? (Noticed Colorado Springs...)
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Thanks for the info, v8volvo - it's great to know I needn't worry about the vertical streaks! :P
How did you prep your block deck? I just scraped the surface of mine with a razor until nothing else would scrape up. The resulting surface is nice and flat, but not very deeply-scoured like yours appears to be. Did you sand it, or use some kind of metal scouring pad?
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I didn't want to fool around with a crappy seal, so I just decided I would get all the right stuff and spend a couple hours cleaning up the head and block gasket surfaces. My arsenal, if I recall, consisted of a flexible razor scraper, a hard blade scraper (which I sharpened to a very fine point on a bench grinder), a roll of emory cloth, a few sheets of ScotchBrite material, and some fine-grit sandpaper.
I got the big stuff with the flexible razor scraper, then went after things with either the scotchbrite or the emory cloth, whichever seemed to work better. Finished with the sandpaper, and used the hard scraper when I needed to really dig tough stuff out. The iron block surface is hard to hurt but you have to be very careful with the aluminum on the head; the razor and the hard scraper will shave that stuff right off and screw everything up. Then I got out a bottle of brake cleaner and bought some lint-free polishing rags, and wiped everything down. (That was, of course, after I had popped the pistons in, since that job gets oil everywhere and that creates a crappy seal. The brake cleaner cuts through the oil and leaves the gasket surface clean and dry).
That was my trick, anyway. I used it both times I've had the head off and no problems. Also did it when I replaced the headgaskets on an old Ford 289 several years ago (when I was 14...jeezus), and I know that thing is still running fine. Hope to check your Rabbit out next time I'm in town!
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I'm rebuilding an engine right now. I'd like to know how you guys deglazed the cylinders? I know it's a tool that is used on a drill but where you I get that tool? Is it a standard soft wire wheel? Is there a particular technique I need to use?
Thanks for the infos :D
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You need what's called a cylinder hone. I think the kind with the hundreds of gritty beads works better for the DIY mechanic's purposes than the 3-stone type, since the bead kind is more tolerant of angle changes (ie, not being completely straight down in the cylinder, which can easily happen if you are trying to hone it with the block in the car).
The hones cost about $80, so unless you think rebuilding engines will be an ongoing, frequent thing for you, you might be better off to rent (as I did, cost me $7 for a day and that's all I needed). Either way, make sure you get one that is designed to work in a bore the size of a VW diesel's--3.01 inches in diameter, if you didn't know.
Depending on how big the "ridge" is at the top of the cylinders, you will also want to buy/rent a "ridge reamer" that will cut the ridge off. Otherwise, when you put the new pistons and rings in, the rings may hit the ridges at the top of the pistons' travel and break, and then you are in trouble. If the ridge is very small (ie, hard to feel), you probably shouldn't worry. And, of course, if it is very very large, it probably means your cylinders are too worn to be re-ringed and you need get the block taken to a machine shop and bored out to the next size up.
George
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And yes, there is a specific technique. Get the guys who rent or sell you the hone to walk you through it. Sounds complicated but actually it is hard to screw up too badly.
You need a pretty big, powerful drill, so if yours is just a little quarter-inch affair, you should get a bigger one of those too.
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Thanks for the infos v8volvo. I think my drill will handle honing. I'll probably rent it, don't plan on rebuilding many engines. I'll be sure to ask them how to properly use it.
Thanks again!
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Although the "econo" rering project for my GTD autocrosser project has been going a bit slow due to crappy weather and time taken away by the long runner intake manifold fabrication, I made a little progress late last week. I was glad I took some extra time to scrub my beadblasted pistons with soap and water, because I discovered one of the rods had previously been assembled on the piston backwards! I put them all back together correctly and with new circlips.
I found little grooves were worn in the pins where they rode on the edges of the rod bushing. My engine builder said it should be OK though. The pins slid in smoothly when the rod was held perfectly square, but I could feel the groove "catch" on the edge of the bushing when there was a little bending force on the rod. I guess I'll just run with it on this block. But it is definitely going to be nice to put in fresh, new pistons and piston pins when I eventually get to my future "dream" engine build.
I also got the block deck looking better than it used to using a rotary scotchbrite pad with my new die grinder toy. :) I used WD-40 to lubricate it and a few times stopped and soaked the surface in it and blotted residue out with a paper towel, which helped keep the pad from from "loading up". Photos below show the surface before the scotchbrite (but scraped as clean as a razor would allow), versus after scotchbriting.
(http://www.imagestation.com/picture/sraid200/peb8dbffc2ed942a416a71346854ff6e9/f04bd9b8.jpg)
(http://www.imagestation.com/picture/sraid200/p59721ed81c838fcf81cab7212c557745/f04bd8a0.jpg)
Equipment used:
(http://www.imagestation.com/picture/sraid200/p03b2be1e00848f885724819ebf65fe81/f04bd999.jpg)
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Looks great, Jake... Those scotchbrite pads really do work well. I tried putting mine on a straight die grinder like yours (pictured), but had a heck of a time trying to keep it on course. It seemed to jump right out of my hands.
Soon after, Harbor_freight (underwriting car projects everywhere...) had a special on their 90 degree air grinder / sander for $14 or something. Seems much easier to control.
Kinda like this, although I don't remember mine being 20k rpm (!)...
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=32046
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While they do an excellent job of cleaning up the surface,they don't do a very good job of keeping it straight.Be very gentle,and go slowly,or you can take off too much material.It's not so bad on a cast block,but I'd think twice about using them on an aluminum head.They will leave a very uneven surface,and gasket failure will result.
If you are going to use one,a right angle die grinder is the way to go.
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veeman: Gotta love harbor freight. :D I'm using their $10 straight grinder! I bought it to polish intake manifold runners and do other stuff with, but haven't had any problems using it for flat surface prep application. I support it ridigly with both hands and when keep it (only very slightly) "on edge" to keep it from darting around.
However, I have had some practice using it on my custom intake manifold project. It's the only tool for the job of runner polishing. The scotchbrite pads work great for welding surface prep too - removing carbon, dirt, oxides. I found it is slow if not impossible to actually remove any of the metal itself with it. I found it is much different than sandpaper in this regard.
wyldman: IMO, on a cast iron surface with an ultra-fine pad, there just isn't anything to be worried about; I don't think you could screw it up if you tried!
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It may be the type of scotchbrite disc you are using,it must be quite fine.
Most scotchbrite discs WILL cut metal.You may not see it,because the surface seems so shiny and smooth,but it will leave a vey uneven surface.
Ask any good automotive machinist.They usually see quite a few heads and blocks,and even manifolds,screwed up by scotchbrite discs.Most gsaket manufacturers and engine rebuilding associattions also have service bulletins out recommending not to use scotchbrite discs.
The easiest way to see this is to try it on an old fender,or body panel.Use the disc to shine it up just like you did the block.Then paint it with some gloss black spray paint.Now hold it up to the light,and look at the surface.Is it flat ? Is is smooth ?
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Forgot to add..........The best way to clean any gasket surface is to carefully scrape off the big stuff,then use a fine wire wheel on a die grinder (make sure it is rated for the RPM).
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The 3 scotchbrite grades I usually see are: medium (brown), fine (red), and extra fine (blue). Standard abraisives, the manufacturer of the abraisive pads, does not recommend using anything but extra fine with a "light touch" for aluminum gasket sealing surfaces.
Standard Abrasives "Engine Block preparation guide": http://www.sa-motorsports.com/blockdiy/blkdiy.shtm
... and a related thread: http://www.vwdiesel.net/phpBB/viewtopic.php?t=2831
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how can one damage metal with a scotch brite? i use a scotchbrite with my air powered die grinder on plastic headlights to get rid of the yellow and it takes probably 15 minutes a light. i couldnt get the scotchbrite to gouge into plastic headlight if i held it in 1 spot for 30 seconds. how could you hurt metal with it?
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how can one damage metal with a scotch brite? i use a scotchbrite with my air powered die grinder on plastic headlights to get rid of the yellow and it takes probably 15 minutes a light. i couldnt get the scotchbrite to gouge into plastic headlight if i held it in 1 spot for 30 seconds. how could you hurt metal with it?
That must be a different kind of scotchbrite.The 3M surface conditioning discs will ruin plastic if you hit it even for a few seconds.
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i know this an old post but some stuff here scared me in a bad way,,, i work in an engine rebuild shop,,,the block guys get scared when theysee us with those schtchbrite discs, they are ok for some things,like valve covers or somethinlike that,very easy to mess somethin up,,i found like 400on up to 1000 grit on a palmsander,with some brakecleen is nice on aluminum,depending on how qwickyou want it cleanwhen i did this on my head,it almost retained the "rainbow" of a freshly milled head,,and use a wire wheel on cast iron,,,,thats what the rebuilders recommend,,stains dont hurt cast,,,,,,,,NEVER never glassbead ring areas of piston,,just dont bead them at all,,,,use either that cold carb dip,or zip strip/"gasket remover" ,,,,cold dip i have had that discolor pistons,,,,but for my tdi build,,i used zipstrip and wood slivers to clean ring lands,,tootthpicks work ok,,DONT use any metal utensial on pistons,,,plastic and wood is ok,,,my pistons cleaned up like new,,but it took 4 --5 applications,tooklike 3-4 hours ,,you mcanuse some toothbrushes,but they melt in the zipstrip after a while,,use it to get the heavy stuff off,,,you do not want to remove any metal from the lands by scraping,,happy building,,70% of engine building is cleaning and prepping,,,a fine wire wheel can be used on aluminum covers and stuff,like seal carriers,,if you are careful and easy on it,,dont stay in one spot for long,,itll dig a little,,carefulwith the rebuild,and itll runa long time with good power potential :D
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The GTD is up and running!!!
Pic of it sitting in grid after its last run at yesterday's autocross:
(http://www.imagestation.com/picture/sraid210/p5239a3ab3623c3c400b3924acbb62487/edb90f39.jpg)
I was up really late the night before getting it ready to race...
(http://www.imagestation.com/picture/sraid210/p635fd4fdd14ba97d11fd44ca6e27a57c/edb90e02.jpg)
What happened was it sprang a MAJOR fuel leak when a make-shift injector return cap popped off after a high-rpm burst (it wasn't the right cap because I misplaced the one that I was supposed to use, but I will never cut corners with a non stock type cap there again.) To make a long story short: there was a 4" diesel GEYSER fountaining out of that fuel return nipple with the engine at idle (Can only imagine how hard it must have been spraying diesel at operating RPM!) When I first popped the hood, it was sopping wet and rained diesel down onto the motor. EVERYTHING under the hood was drenched with DIESEL. It was steaming like a radiator boil over, but was actually HOT diesel. What a mess. Anyway what I think happened was that some of it got onto the clutch and contaminated it. It couldn't hold the full boost power.
Here is a shot of the contaminated pressure plate (notice the discoloration):
(http://www.imagestation.com/picture/sraid210/pa0dae5b68a7f24012d15151f2c13481a/edb90ea2.jpg)
Everything cleaned up nicely with a die grinder powered scotch brite pad. It's a racing, sintered copper clutch friction material. Pretty cool it just cleans up after being contaminated like that. Here is what it and the flywheel looked like after air-powered scotchbrite cleaning:
(http://www.imagestation.com/picture/sraid210/p3899194b11320e3c8b588ab2ffeeaae0/edb90df3.jpg)
That did the trick to get the clutch to hook up like new.
I'm very pleased to report that the performance at the autocross practice yesterday was limited by the driver and not by the car! :lol:
I think it's official: the over-revved head incident has now finally been overcome. (Hmmm... I might have to start up a new thread next time) I'm very excited about campaigning this car in the rest of the '06 racing season... :) Oh and by the way the engine and freshly rebuilt K24 turbo are just performing superbly.
Next event is August 12-13 at the SCCA National Tour in Packwood, WA. Wish me luck! (With only one practice event on this car in two years, I need it.)
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Oh by the way here are a couple shots from inside the motor concluding the engine prior to the getting the car running again...
pistons installed:
(http://www.imagestation.com/picture/sraid210/pfaa74be4c8c1cf6097b1c55b7fd96211/edb8f352.jpg)
head prepped:
(http://www.imagestation.com/picture/sraid210/p31e9783a32bf4833a099025c115d3561/edb8f5c4.jpg)
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Way to go, Jake! Looks like the old "drive" is still there, eh?.... staying up until all hours redoing the clutch. Wow.
How do you like that four puck clutch? I've got the same copper / ceramic type six puck in my gasser FSP rabbit and it was a bit "digital" (on/off) until it really got bedded in after some use.
How does the K24 setup you're running compare to the previous turbo? Driving impressions? Did you end up raising the boost per the rules?
Great work on the rebuild...looks super clean. Is that a valve mark I notice in piston #4 in the pic?
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I haven't done a back to back comparison of the K24 versus Garrett yet, but am very pleased with the current performance of the motor with the K24.
The piston tops were well covered earlier in this thread...
http://vwdiesel.net/phpBB/viewtopic.php?t=406&start=28
4-puck clutch observations are noted here:
http://vwdiesel.net/phpBB/viewtopic.php?t=164
I've got some sort of coolant leak. I've gotta bust my ass to make the national tour this weekend. I don't feel particularly well prepared for it... :? All my wrenching and tuning time got sucked away from other things last weekend.