How much blowby it too much? - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• How much blowby it too much? by Quantum TD on 16 Feb, 2008 16:22
• Hey guys. Just wanted to get some thoughts from those who've got blowby, and at what point I should give up and re-ring/re-bore the block. Here's what's happening:
  
  1982 Rabbit Caddy Diesel. 220k on the body, less on the motor (I'm told). I bought the truck and the PO told me it was a runaway, and wasn't sure at what point it was shut down (he bought it from the guy it ranaway on). Anyway, I went out today (after buying the truck 3 months ago), and started it up. It pretty much fired right up. But, when I removed the oil-filler cap, white smoke was a puffiing out, and oil was being forced out of the dipstick tube.
  
  After further examination, I realized that the dipstick tube was an aftermarket, and the pan was overfull by about 2- 2& 1/2 quarts. So, I drained the oil, and refilled with just 4& 1/2 quarts. After doing that, the oil was no longer shooting out of the dipstick tube. So, one problem solved.
  
  Then,  I put an oil baffle over the cam to keep the oil down. Then, I started it back up to see how she'd do. The smoke factor was about the same (obviously). The strange thing is that the blowby doesn't seem that much worse than other car's that I've owned which had good compression. There's just that white smoke, and I'm wondering if there isn't some moisture in the block from sitting for so long (been sitting about 1-2 years). Before that, the motor sat for about 5-8 years.
  
  Another strange thing is that the intake was pretty clean. There was about an ounc of oil on the bottom of the intake, but the filter was dry (not saturated), and it looks like the filter has been in for some time, as the outside was pretty dirty. It looks like there is about 2-4k on the filter.
  
  Anyway, I guess I wanted to ask a few quick questions about dealing/living with blow-by. Basically, I'm not planning on keeping this motor in the truck very long, but I may try to reuse the bottom end if possible on another car for a friend. My main questions are:
  
  1) Is it possible/advisable to just re-ring the bottom end (if the cylinder's don't look to bad)? Or is it a safe bet (with any blowby) that the cylinders need to be re-bored and oversized pistons must be used?
  
  2) I'm thinking of driving this motor for a while. With the oil baffle on there, is there still a chance of a runaway? Obviously, there is some blow-by. But is it possible that the 2-3 quarts of excess oil caused the car to runaway?
  
  I've never had to deal with blow-by before, but it seems like every car I work on now has *** rings.
• #1 by rabbitman on 16 Feb, 2008 18:09
• I once cosidered buying a diesel caddy, untill I looked at it. I was hoping to see it start cold so I could check blowby but she was driving it around when I got there. So, after walking around in the cloud of white smoke trying to find the caddy I stumbled into something that was shaking like an earthquake. It was the caddy. I located the oil cap and tried to see if it had a baffle but instantly yanked my head back to avoid getting oil sprayed in my face. Then I thought "she did tell me the throttle stuck sometimes", runaway? After nearly smashing my fingers putting the oil cap back on the shaking motor, I decided the motor mounts weren't very good. I then attempted to check the coolant level but could not see into the tank on account of the fine, white, sweet smelling mist hitting my face. I says to the girl "it's out of antifreeze" so she dumps maybe a half gallon of water in and puts the cap on, I take the cap back off and look in and it was still empty so I shut it off. It's well below freezing out, but the water will leak out the gaping hole in the water pump long before it freezes. Then she tells me the puddles of oil on top of the engine and tranny was from the vacuum pump coming loose and lifting out of the hole and spraying oil everywere :shock: So the oil pump probably wasn't turning either. I didn't buy the thing.
  
  So maybe your car has a cracked head or block from the PO overheating it. It could be that there's cracks between the coolant jacket and intake port(s), I've never heard of it but it might be possible. Is the white smoke coming from the exhaust and/or valve cover? Hopefully it's not as bad as that. Good luck!!
• #2 by Quantum TD on 16 Feb, 2008 21:09
• Nope. No overheat. It runs fine: maybe some clogged injectors. It just smokes out of the valve cover when you take the oil cap off. It's not plumes either, just a steady but faint puff-puff-puff. I'm certain it's just blowby (note that: "just blowby").
  
  It may be livable, if only for a while. I'm thinking with the oil baffle and perhaps some creative hose-routing for the block breather, coupled with a strainer of some sort, I can run it for a while.
• #3 by dieselsnowmobile on 17 Feb, 2008 12:24
• Do a compression test.  The amount of blow-by is not important if you have good compression.    Most likely, the more blow-by you have, the lower compression you should have, but doing a compression test will give you the exact number you need to tell if you need to rebuild the engine.
• #4 by blkboostedtruck on 17 Feb, 2008 13:28
• my buddys rabbit he just bought if you take the oil cap off when it's running it will race off till you put it in gear and dump the clutch to stall it!
  thats the worst case i've seen?
  so if it don't run on it's own oil then it's fine till it does then rering it!
  thanks Duane
• #5 by v8volvo on 19 Feb, 2008 20:34
• Since the crankcase breather tube dumps into the intake after the air filter, it wouldn't surprise me if the filter wasn't that oily.
  
  Because diesels run such high compression, it's almost inevitable that there would be some blowby. My folks' '04 Passat TDI does a steady puff-puff that you can easily feel with your hand if you take the oil fill cap off, and has done so since new. I've never found a diesel that didn't have a little crankcase pressure in it. I think your blowby might not actually be that bad at all -- it's possible it was just way too overfilled with oil, which could cause runaway too.
  
  If the engine's cold, and there's moisture in the block, white smoke would not be surprising either. How does it run? I would make sure the oil level is right and all other fluids are OK and get it out on the road and really warm it up, then take the cap off and see if you're still getting white smoke.
  
  When I got my Rabbit, with 220k on it, it was using a quart every 100 miles, but it started and ran great and blowby was not bad. Tore it down and discovered the rings had all lost their spring. Did a quick hone and re-ring, slapped it back together, and problem was solved...but blowby was the same. I have full compression and use zero oil whatsoever, but still feel a little puff when I take the oil cap off. If it starts OK, runs OK, and doesn't drink oil, it might just be fine, and need a more careful oil change next time...
• #6 by burn_your_money on 19 Feb, 2008 20:56
• Positive crankcase pressure is normal on all vehicles (which is the puffing). It is what keeps dirt and crap out of the air and also helps the seals seal. It is when it is accompanied by a mist of white smoke or oil that it is a concern.
  
  Since you are familiar with runaways I'll assume you know how to stall the engine in the event of one so I would say drive it and keep a close eye on the oil level. It is definitely likely that it is moisture evaporating from the engine.
  
  I bought a runaway engine once and it fired right up and seemed to run fine as well. I never drove it, just parted it out. When I tore the bottom end apart I found that the cyl #2 top compression ring was worn down to about 1/16" wide which is what caused the runaway.
• #7 by v8volvo on 19 Feb, 2008 21:01
• And to answer your questions -- runaway could still happen with the baffle on there but it's less likely. And yes, I believe it could just be caused by an overfull sump.
  
  Second, regarding how far you have to tear into the engine if you decide you have ring problems, it's always unfortunately a decision you kind of have to make after you've seen what things look like on the inside... if the engine has under 200k and the compression isn't shot, chances are good you'll be fine just honing and re-ringing. You can do all that easily with the block in the car, just pulling the head and the pan. I did it in an easy weekend (having collected all the parts and tools beforehand though), at a total cost of about $100. Since then I've driven that engine cross-country twice (Seattle to Colorado to Boston, then back from Boston to Colorado to Los Angeles to Seattle), and lots of other driving besides, 25,000 miles in all, without a bit of trouble ever. Still no oil use and full compression. I don't expect it to last 200k, but I don't need or want it to. 245k on the original block, pistons, etc, only new things are rings, valves, and valve guides/seals. And honed it.
  
  However, I got lucky with an engine that was basically in OK shape other than having shot rings. If you get in there to re-ring it and discover your cylinders have deep scoring, there's a big cylinder wall wear ridge at the top, your pistons are beat, or something, you'll have to pull the block and have it bored, do oversize rings and new pistons, the whole deal. But if the pistons don't have too much play in the ring lands, you clean them well, get a good hone on the cylinders and there's no scoring and the ridge isn't too huge (big ridge means big taper wear in the bores, and could break off your new rings), go for it. A re-ring is never a real rebuild but if you just want to drive it for a while and not spend much time or $$ then it will often do the job.
• #8 by Quantum TD on 19 Feb, 2008 21:23
• Yeah. I'm gonna drive it a while and see what happens. The pressure isn't so bad, but I will test compression to see what I get.
  
  As for honing and re-ringing, I'm leery of it these days. I did it on a 200k+ Passat 2.0 bottom end once and it was fine. Recently I did it to a 1.6 diesel motor with clean cylinder walls, but a noticeable ridge at the top (supposedly only 73k on the motor, but NO compression). I started the car up afterwards and I have a hammering sound that goes away when RPMS are pushed over 2900. At this point, it's either piston slap, bad wrist pins or I dunno what. Either way, I'm not happy about it, and in my mind, the only real solution was to bore and put in OS pistons. I tried to go cheap and it backfired. Maybe it's something simple, but no-one here seems to have any insights as to the hammering noise. It seems to defy logic (present at idle, goes away with higher RPMs).
  
  It just seems like these older 1.6 motors had a real poblem with cylinder wall wear. It seems like everyone I look at these days has a pronounced ridge at the top. I'd like to chalk it up to poor lubrication on the 1.6NA motor, since the only thing that lubricates the pistons is the oil being slapped around the case, but my 1982 1.6TD motor with about 140K on it (and oil coolers lubing the cylinders) looks about the same as every other used 1.6 motor I've ever seen, in regards to the ridge. So: *** materials? Who knows.
  
  I'll run this bugger for a while and see what comes of it. At least it runs and has SOME compression. The last motor I fooled with had zero compression (the rings were all worn, and the #2 rings were cracked on every piston).
• #9 by myke_w on 20 Feb, 2008 06:51
• Quote from: "Quantum TD"

  
  As for honing and re-ringing, I'm leery of it these days. I did it on a 200k+ Passat 2.0 bottom end once and it was fine. Recently I did it to a 1.6 diesel motor with clean cylinder walls, but a noticeable ridge at the top (supposedly only 73k on the motor, but NO compression). I started the car up afterwards and I have a hammering sound that goes away when RPMS are pushed over 2900. At this point, it's either piston slap, bad wrist pins or I dunno what. Either way, I'm not happy about it, and in my mind, the only real solution was to bore and put in OS pistons. I tried to go cheap and it backfired. Maybe it's something simple, but no-one here seems to have any insights as to the hammering noise. It seems ot dfy logic (present at idle, goes away with higher RPMs).
  
  It just seems like these older 1.6 motors had a real poblem with cylinder wall wear. It seems like everyone I look at these days has a pronounced ridge at the top. I'd like to chalk it up to poor lubrication on the 1.6NA motor, since the only thing that lubricates the pistons is the oil being slapped around the case, but my 1982 1.6TD motor with about 140K on it (and oil coolers lubing the cylinders) looks about the same as every other used 1.6 motor I've ever seen, in regards to the ridge. So: *** materials? Who knows.

  
  
  I have a few ideas on this..
  
  The TDI AHU motors are lubricated in the same manner and don't really have "premature wear" problems. I've seen many in my own shop with as much as 250 - 300k miles with no substantial oil consumption or power loss. The owners of such vehicles are also (in my experience) a bit more vigilant and particular when it comes to service. The almost always ask what kind of oil I intend to use etc.
  
  In my mind there are three issues at hand concerning 1.6 TD/D cylinder and likely intermediate shaft wear.
  
  1) Odometer Discrepancy
  the odometer that came in any car with a 1.6 diesel is susceptible to the plastic counter gear breaking and thus misreporting mileage - in turn inspiring people to say things like "FS 1.6 TD with 140k" when in fact the motor could and likely does have far more miles. My latest example- I just parted out a mk2 1986 Jetta TD whose ODO read 120k.. the thing was a rusted pile of scrap, holes everywhere.... 120k miles??? yea right, more like 320k miles.. I could go on for days about this.
  
  2)*** Oil
  So many of these cars have been owned by multiple owners who may or may not have any idea about what oil is / was appropriate for the power plant. It is a well known fact that using a NON Compression Ignition rated oil in a diesel motor is a recipe for disaster. Diesel rated oils have an additive package with the appropriate detergents to hold the soot in suspension by allowing it to combine with the agents in the additive package, and without it, the soot becomes a free agent, an abrasive if you will..
  
  It is my belief that if you ran a 1.6D or TD on a good modern synthetic diesel specific oil and did regular OCI's you could easily get 300k out of it in regular highway service.
  
  3) Abuse & Neglect
  We all know that not everybody drives like grandma Fran. In fact a lot of people that have or have had TD's beat them like redheaded stepchildren, myself included. We have also all seen the obvious results of neglect - not changing oil at regular intervals, letting oil get low etc.
  
  ***********************************************
  
  Anyway, I can't 100% agree that we can blame the materials without first considering the other options. There are too many other variables at work.  
  
  At some point I intend to do a bone stock rebuild of a TD for my caddy, fix the ODO with Ken Borth of Overseas speedo and then run nothing but full syn after break in and see how long it goes.. I'll report back in 10 years or so
• #10 by 91MF on 20 Feb, 2008 15:38
• Quote from: myke_w

  Quote from: "Quantum TD"

  
  2)*** Oil
  So many of these cars have been owned by multiple owners who may or may not have any idea about what oil is / was appropriate for the power plant. It is a well known fact that using a NON Compression Ignition rated oil in a diesel motor is a recipe for disaster. Diesel rated oils have an additive package with the appropriate detergents to hold the soot in suspension by allowing it to combine with the agents in the additive package, and without it, the soot becomes a free agent, an abrasive if you will..
  
  

  
  
  i have only had my td for a short while and have only done one oil change. i put 5w40 castrol syntec in. bad move?
• #11 by myke_w on 20 Feb, 2008 18:29
• Dunno, does syntec have a "C" rating on the bottle?
  
  BTW, This isn't the kind of thing that happens in one OCI, it's more an over the lifetime of the motor phenomenon.
• #12 by blkboostedtruck on 20 Feb, 2008 19:20
• in the Bently man. it calls for (oil labeled "for service API/CC" or " for service API/CD" for standard diesel engines, or labeled "for service API/CD" in turbo diesels.
  
  I never  understood what that meant?
  one oil i have in my hand says = castrol syntec 5w-50 full syn. API service SM,SL,SJ,CF  
  
  now since it has the CF it will meet the criteria because the"F" is higher then the 'C' and 'D' or am i understanding this wrong?
  thanks Duane
• #13 by jtanguay on 20 Feb, 2008 19:37
• CD  Obsolete Introduced in 1955. For certain naturally aspirated and turbocharged engines.  
  
  CF  Current  Introduced in 1994. For off-road, indirect injected and other diesel engines including those using fuel with over 0.5% weight sulfur. Can be used in place of CD oils.
  
  i think nearly all synthetic oils are CF rated... but are they that good at keeping the soot suspended? who knows...
• #14 by Vincent Waldon on 20 Feb, 2008 21:17
• OK, if we're gonna geek out on oil designations what the hey...  let's go to the source... the American Petroleum Institute:
  
  http://vincewaldon.com/images/documents/ase_oil_specs.pdf
  
  Page three... way more then you ever want to know about what diesel standards came in when, and what they were replaced with.
  
  
  I used to think the "S" was for Spark ignition, and the "C" for Compression ignition, but no...... evidently S is for Service, and C is for Commercial.  
  
  Guess I drive a commercial vehicle... go figure.