VWDiesel.net The IDI, TDI, and mTDI source.
General Information => Troubleshooting => Topic started by: EcoMod on November 21, 2008, 05:49:17 am
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Well, I pulled my lil 1.6td head last night, in the dark.
I found cracks in the center of each combustion chamber between the valves.
This tends to quite common, so I hear?
My question is: Is this an automatic head replacement? I do not like welding on cylinder heads, especially diesels.
the good news is that the only bad this found on the block so far is a little rust at the top of the cylinder wall(from sitting)
:roll:
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My understanding from everyone on the boards, reading on the internet, and my Bentley manual is that cracks up to 1mm are acceptable, but 2mm is too much. Others might have actual experience running heads with cracks larger than 2mm. My head has cracks between the valves but they are <1mm so I'm using the head again.
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The cracks between as mentioned are fine if 1mm or under.
I've seen like maybe 3 heads that were not cracked..
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Thanks for the info. I have yet to get a manual for the mk2's. I will need one before I start putting this thing back together.
I guess my plan of attack will be to take this head to the machine shop and get it checked for cracks and distortion. If it is not bad, I will get it ever so slightly resurfaced, reseat the valves and put in some new lifters. slap it back on with new valve seals, ARP headstuds and headgasket.
Just going to have to weigh the outcome of cheap vs. my usual tuner methods, which turn out to be non wife friendly. :wink:
I have seen stock, high mileage jetta diesels going for over 2,000usd.... is this pretty common? If I have 2k into this car after a partial rebuild and cosmetics I shouldn't too upside down on it.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
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I had to buy a new head because my cracks grew too large and my coolant became pressurized.
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I had to buy a new head because my cracks grew too large and my coolant became pressurized.
Just run it with the radiator cap off!!!
Just kidding^^^^
The mechanic that did my head, peened the cracks slightly to prevent them from closing. Later found out that it was a prothe head, and the valve guide holes were all outa wack.
What was the problem before you pulled the head? were u suspecting a damaged head?
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Many times a large crack doesn't just mean a large crack,... leaking or not.
It sometimes means the head was overheated and is probably warped.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Talking about these cracks btween the valves I think I've had 7 different heads over the years and they were all good and all had cracks between every valve. I just got a new Top-Line head for this engine which isn't in the car yet and I'm wondering what actualy causes the cracks in the first place and how long it will take to get cracks in this new one, evidently they appear no matter what you do, any thoughts :?:
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I had to buy a new head because my cracks grew too large and my coolant became pressurized.
Just run it with the radiator cap off!!!
Just kidding^^^^
The mechanic that did my head, peened the cracks slightly to prevent them from closing. Later found out that it was a prothe head, and the valve guide holes were all outa wack.
What was the problem before you pulled the head? were u suspecting a damaged head?
The new head i got is a prothe head. I hope it works better than how you said :( I spent a lot of money on it. (well relatively cheap in the realm of engines but expensive to my small wallet)
I had already had that head off and on about three times because i kept nievely trying to fix bad starting.
The compression was terrible due to toast rings and the cracks between the valves went into the coolant.
Also, now that i've had it off and looked at it, all the prechambers are cracked.
I hopefully fixed this problem... all the parts i bought were extremely cheap except for the HG and ARP's. Time can only tell.
MY thoughts on the crackin is perhaps it's just from temperature changes?
Anyone know about these cracks on heads apart from VW?
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Talking about these cracks btween the valves I think I've had 7 different heads over the years and they were all good and all had cracks between every valve. I just got a new Top-Line head for this engine which isn't in the car yet and I'm wondering what actualy causes the cracks in the first place and how long it will take to get cracks in this new one, evidently they appear no matter what you do, any thoughts :?:
i think it has to do with the fact that the swirl chamber takes up a lot of room, and leaves little meat between the valves. plus the fact that they are dissimilar metals (different expansion rates-aluminum vs inconel). thats why the TDI's don't have these cracks between the valves.
i wouldn't be too concerned with the prothe head. i would highly recommend going with the 1.9 MLS gasket & arp head studs (which you have). if you plan on turning up the fuel and running the motor really hard, it might not last though...
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Talking about these cracks btween the valves I think I've had 7 different heads over the years and they were all good and all had cracks between every valve. I just got a new Top-Line head for this engine which isn't in the car yet and I'm wondering what actualy causes the cracks in the first place and how long it will take to get cracks in this new one, evidently they appear no matter what you do, any thoughts :?:
i think it has to do with the fact that the swirl chamber takes up a lot of room, and leaves little meat between the valves. plus the fact that they are dissimilar metals (different expansion rates-aluminum vs inconel). thats why the TDI's don't have these cracks between the valves.
i wouldn't be too concerned with the prothe head. i would highly recommend going with the 1.9 MLS gasket & arp head studs (which you have). if you plan on turning up the fuel and running the motor really hard, it might not last though...
That makes pretty good sense about different metals, I never heard it mentioned before. I guess they do have to be made out of some pretty good stuff and as tight as they fit expansion rates could probably cause it.
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Rehab. Someone had to say it. :roll:
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When you have a cold engine, be gentle with the gas pedal. More fuel, more heat. Cold metal with a thin layer of very hot metal will prevent that hot metal expanding fully, hot metal yields as hot metal is more plastic than cold metal. When everything cools down, tha yielded metal now has a tensile prestress, cracks. Repeat a few hundred times, wonder why there is a bloody great crack in it. The following gives a idea to the principles, but me being a Civils Bod, it might be on too big a scale. 8)
http://www.fhwa.dot.gov/BRIDGE/steel/01.cfm
When that engine is nice and hot, THEN give it some welly! :twisted:
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Took my head into machinist Friday.
There's a hairline crack between valves on cyl #3. Will be pressure tested this coming week. Don't know how far up the felts this crack runs, but he'll look at. He said that there is likely nothing wrong with it - lots of meat between crack and water jacket? Said he'd raither not try to fix it with a drill and spot weld...may create a problem where there is none.
He's done good work for me in the past.
Does this check out with your experience? Seems to me that it does...
... minus 45 windchill here now - gotta go plow - dreaming of summer!
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I haven't seen a head yet without some cracks between the valves, holding pressure or not. It seems it would have to be awfully deep to hit the water jacket.
If I had to guess I'd say once the crack propagates right across from side to side it's relieved the stress and doesn't go any "deeper" up into the meat of the head. That thicker area wouldn't be flexing as much as the thin web between the valves so the crack won't wiggle it's way up.
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Thanks.
Thats what I figured.
I'll let you know what happens.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Yes I also agree that the size can't be the determining factor, just a rough guidline. The thing I would like to know is how they actualy do pressure test a head in the first place. I've had some tested for myself and we sent them to the machine shop all the time when I was a mechanic but I never ever saw a pressure testing tool. I just can't visualize a tool that would be adaptable enough to be able to seal virtualy every kind o head there is considering bolt patterns, coolant ports and such. It's probably a pretty simple tool in reality if ou could see a picture of one. I just wonder if it is something we could rig-up for at least just our VW heads. We all seem to have the same problems like this and it could save us a lot of time in the shop, money and worries if we could do it ourselves.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Yes I also agree that the size can't be the determining factor, just a rough guidline. The thing I would like to know is how they actualy do pressure test a head in the first place. I've had some tested for myself and we sent them to the machine shop all the time when I was a mechanic but I never ever saw a pressure testing tool. I just can't visualize a tool that would be adaptable enough to be able to seal virtualy every kind o head there is considering bolt patterns, coolant ports and such. It's probably a pretty simple tool in reality if ou could see a picture of one. I just wonder if it is something we could rig-up for at least just our VW heads. We all seem to have the same problems like this and it could save us a lot of time in the shop, money and worries if we could do it ourselves.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Yes I also agree that the size can't be the determining factor, just a rough guidline. The thing I would like to know is how they actualy do pressure test a head in the first place. I've had some tested for myself and we sent them to the machine shop all the time when I was a mechanic but I never ever saw a pressure testing tool. I just can't visualize a tool that would be adaptable enough to be able to seal virtualy every kind o head there is considering bolt patterns, coolant ports and such. It's probably a pretty simple tool in reality if ou could see a picture of one. I just wonder if it is something we could rig-up for at least just our VW heads. We all seem to have the same problems like this and it could save us a lot of time in the shop, money and worries if we could do it ourselves.
you know... i never really thought about what the pressure testing tool would look like. and yes it would need to be able to seal very well. perhaps the best testing method would be to bastardize a 1.6/1.9 block, seal up the piston side, and the coolant ports, and do it that way? wouldn't need a new gasket each time because its not under combustion pressures. this could also test valve leakage as well.
does anyone have any input on what the whole pressure testing procedure is? i'm very curious now! :lol:
edit: a quick search revealed this (http://www.amacengineering.co.uk/OtherServices/PressureTesting.htm) site. looks like a universal tester. and also this (http://www.daverushton.co.uk/pressure.htm) tester. looks to be quite elaborate and very adjustable for any kind of head.
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doesn't matter how big the cracks are, if they leak they leak.. if they dont leak, then you're fine. getting it pressure tested isn't too much coin if you want some peace of mind.
would suck if you bought a new head and your head was fine. but if you have the money for it, it's not a bad thing. only if you buy an inferior product.
Yes I also agree that the size can't be the determining factor, just a rough guidline. The thing I would like to know is how they actualy do pressure test a head in the first place. I've had some tested for myself and we sent them to the machine shop all the time when I was a mechanic but I never ever saw a pressure testing tool. I just can't visualize a tool that would be adaptable enough to be able to seal virtualy every kind o head there is considering bolt patterns, coolant ports and such. It's probably a pretty simple tool in reality if ou could see a picture of one. I just wonder if it is something we could rig-up for at least just our VW heads. We all seem to have the same problems like this and it could save us a lot of time in the shop, money and worries if we could do it ourselves.
you know... i never really thought about what the pressure testing tool would look like. and yes it would need to be able to seal very well. perhaps the best testing method would be to bastardize a 1.6/1.9 block, seal up the piston side, and the coolant ports, and do it that way? wouldn't need a new gasket each time because its not under combustion pressures. this could also test valve leakage as well.
does anyone have any input on what the whole pressure testing procedure is? i'm very curious now! :lol:
edit: a quick search revealed this (http://www.amacengineering.co.uk/OtherServices/PressureTesting.htm) site. looks like a universal tester. and also this (http://www.daverushton.co.uk/pressure.htm) tester. looks to be quite elaborate and very adjustable for any kind of head.
Yea a block probably would be a good place to start with to make the tool, assuming its not cracked too :lol: I wonder what kind of pressures would be required to do this that would reveal the leaks, use with an air compressor and water maby. Mine only goes to 110 I think. But then again since we're only concerned with the coolant passages an they're pressures, 20 psi might do it. Hell I think I got enough stuff around here to do this including an old N/A block, new 3 notch fiber gasket I'll never use for anything else, plenty of head bolts 11 and 12 m/m and a couple heads too. The pressure hookup shouldn't be too difficult. I believe I might do some experimenting with this idea soon, I would like to know what pressures the machine shop uses though but I'd be ashammed to tell them what I'm doing :lol:
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Head:
Head has some serious problems. Valves are so loose that you could use them as a kitchen blender! Valves and guides are gone...and the seats. There is quite a bit of stress showing on the cylinder plugs - lines showing up some pre-crack warnings. And then he didn't even do a pressure test or check for warpage. For the price of doing all this he already found a factory re-built/re-conditioned head (including cam) without all the stresses. He's putting it back together for a core trade-in. I'm sure it would work...but then again I don't want to have to pull it after a couple of years on the water. Put the best on that I can afford...and after all, in comparison with a new outboard, for example, it's still a steal...
Pressure Testing:
I asked him his method. Like he said they do tests on everything from CATs to VWs and there's no one machine that could do it all. Over the years they have cut small 3/8" plates that match most engines and are bolted into the head studs. Between the plates and the head they place a piece of rubber innertube just larger than the holes and tighten them down. They have an inflateable plug for the outlet and another one for the inlet which fits around an airhose fitting. They inject the water jacket with 110 psi of air and then slather on a water-soap mix that readily shows any leaks. Pretty ingenious and straight-forward if you ask me. Wouldn't take much to make up something like that for your 1.6s!
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... minus 45 windchill here now - gotta go plow - dreaming of summer!
Summer is like 4-5 days that far north, right? :lol: :lol: :lol:
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Lots of people here say that we have two seasons. 9 months of winter and 3 months of tough sledding! :)
Taking the block in for assessment this a.m..
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Looks like the block checks out very well. Makes me crazy-happy!
A word on caution on pressure-testing to follow up on the discussion here...
IF YOU PRESSURE TEST YOUR OWN HEAD MAKE CERTAIN THAT YOU DO NOT STAND IN FRONT OF THE ENGINE PLUGS!!! The machinist showed me a place where one had shot out of a damaged engine he was testing. Went right through the wall...
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Looks like the block checks out very well. Makes me crazy-happy!
A word on caution on pressure-testing to follow up on the discussion here...
IF YOU PRESSURE TEST YOUR OWN HEAD MAKE CERTAIN THAT YOU DO NOT STAND IN FRONT OF THE ENGINE PLUGS!!! The machinist showed me a place where one had shot out of a damaged engine he was testing. Went right through the wall...
Thank's for the heads up about the plug coming out. I will definately keep that in mind if I get to experimenting with this.
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If you haven't decided what to do yet here is some inspiration...
(http://i49.photobucket.com/albums/f279/edmcclung/IMG_7242.jpg)
(http://i49.photobucket.com/albums/f279/edmcclung/IMG_7241.jpg)
(http://i49.photobucket.com/albums/f279/edmcclung/DSC05029.jpg)
:twisted:
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THAT is BEAUTIFUL!
I'm waiting to see how the bottom of the cyinders check out. But they should be fine. I'll get a rebuilt head.
Is this head your own or a rebuild?