4.2 engine failure after timing belt change
12-15-2010, 06:22 PM
#1
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4.2 engine failure after timing belt change
My local garage that takes care of my A-8 I had do a timing belt maintainance change at 105K. He called me after completed the job he started the car, said the cam tensioners were defective and worn out and the car jumped time and valves hit the heads.. I now have a junked engine says wants to show me the malfunctioning cam tensions and why this happened.. Before he did the work, I mentioned that the car had the intemittent clacking noise at start up when the car sat for a while but not all the time. Can anyone advise me here. I can't believe that the cam tensioners could get the car so way out of time that there would have been catistrophic interference or any interference for that matter. Advice please
12-15-2010, 07:01 PM
#2
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They are lying to you. They screwed up the belt timing..the only thing that could cause piston contact with valves AND it had to be running to do the damage, so they started it without double checking the belt timing or didn't tension the belt.
Almost all A8's make a little chain noise at cold start up...not really an indication of bad cam chain tensioners, just a little spring loaded pin that is supposed to hold tension on chain till oil pressure builds up ...very common and no damage as a result.
I have never heard of such damage done from even a completely failed cam chain tensioner. Only heard of this from a broken timing belt when engine was running. The chain in a tensioner or the internal cam gear would have to break, to throw timing out far enough to do this. It would be a one in a billion chance for cam tensioner to do this...it is not the nature of their design. The worst I've ever heard was getting slightly out of time and throwing a code...NOT piston contact with valves.
I have NEVER heard of anything close to this.
TOO MUCH of a coincidence...they did this!
Almost all A8's make a little chain noise at cold start up...not really an indication of bad cam chain tensioners, just a little spring loaded pin that is supposed to hold tension on chain till oil pressure builds up ...very common and no damage as a result.
I have never heard of such damage done from even a completely failed cam chain tensioner. Only heard of this from a broken timing belt when engine was running. The chain in a tensioner or the internal cam gear would have to break, to throw timing out far enough to do this. It would be a one in a billion chance for cam tensioner to do this...it is not the nature of their design. The worst I've ever heard was getting slightly out of time and throwing a code...NOT piston contact with valves.
I have NEVER heard of anything close to this.
TOO MUCH of a coincidence...they did this!
12-16-2010, 03:32 PM
#5
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I would make them prove their claim of what happened to the engine. If they have pulled the cam tensioner already, then they've destroyed the evidence (so to speak) already.
If the engine is still assembled, in case you are not familiar with proper cam belt and chain timing, I included 4 drawings.
The 1st shows crank pulley set at TDC (which is locked in place during belt change), before checking the following.
The 2nd shows timing belt cam gear positions at TDC cylinder #5 (where engine is set for belt change and to check internal cam gear timing). The 4 holes on the gears should be dead level with large holes pointing inward at each other.
The 3rd shows cam gear lock installed (used during belt cahnge), proving proper belt timing at TDC cylinder #5.
The 4th shows proper timing of internal cam gears with timing marks lined up (while belt timing is as shown in #1 & #2). The cam tensioner in question is mounted between these gears, with arched piece in contact with chain.
If they have left the timing belt in place (as they should, if they're not lying), in proper timing as shown, all they have to do is remove the valve cover to show you the failure.... chain, tensioner and gears. If they have disassembled things farther than this, it could only be to cover up what they really did.
If they show you something similar or anything about the damage, please take photos and post...even cell phone pics, if you can.
I'd love to see this for myself. Thanks.
P.S. It's possible that they could have already altered things to cover they're tracks. And, of course, it might be possible that it happened the way they said, but I sincerely doubt that...to suddenly fail catastrophically right after a properly done belt job...not likely. They probably used your mention of noise on cold start up (as I stated, very common...I've always gotten that)as an "out" for their screw-up.
If the engine is still assembled, in case you are not familiar with proper cam belt and chain timing, I included 4 drawings.
The 1st shows crank pulley set at TDC (which is locked in place during belt change), before checking the following.
The 2nd shows timing belt cam gear positions at TDC cylinder #5 (where engine is set for belt change and to check internal cam gear timing). The 4 holes on the gears should be dead level with large holes pointing inward at each other.
The 3rd shows cam gear lock installed (used during belt cahnge), proving proper belt timing at TDC cylinder #5.
The 4th shows proper timing of internal cam gears with timing marks lined up (while belt timing is as shown in #1 & #2). The cam tensioner in question is mounted between these gears, with arched piece in contact with chain.
If they have left the timing belt in place (as they should, if they're not lying), in proper timing as shown, all they have to do is remove the valve cover to show you the failure.... chain, tensioner and gears. If they have disassembled things farther than this, it could only be to cover up what they really did.
If they show you something similar or anything about the damage, please take photos and post...even cell phone pics, if you can.
I'd love to see this for myself. Thanks.
P.S. It's possible that they could have already altered things to cover they're tracks. And, of course, it might be possible that it happened the way they said, but I sincerely doubt that...to suddenly fail catastrophically right after a properly done belt job...not likely. They probably used your mention of noise on cold start up (as I stated, very common...I've always gotten that)as an "out" for their screw-up.
Last edited by silverd2; 12-16-2010 at 04:51 PM.
12-17-2010, 05:33 AM
#6
Is this 32v or a 40v? did a cam chain tensioner fail or the belt tensioner, or a roller? the chain tensioner is seen in the top middle pof the last picture above.
The 40v, I know, can make a few clacking sounds at startup as the cam chain tensioners pressurize. The 32v probably does this too. If one of these fails the engine will get pretty messed up and probably need a new head.
If the cam belt tensioner failed they should have noticed this when they worked on the belt change. These parts should be inspected, the rollers (and possibly the tensioner) replaced and any issues addressed. It'd take an idiot to miss a problem in this area during a timing belt job.
If your problem is actually one of the chain tensioners in the head the shop can probably not be held responsible. A timing belt job does not address any issues with the chains and tensioners under the cam covers and these parts can indeed fail. However it should only damage one head and it should be possible to replace the head more cheaply than the entire engine.
-Joel.
The 40v, I know, can make a few clacking sounds at startup as the cam chain tensioners pressurize. The 32v probably does this too. If one of these fails the engine will get pretty messed up and probably need a new head.
If the cam belt tensioner failed they should have noticed this when they worked on the belt change. These parts should be inspected, the rollers (and possibly the tensioner) replaced and any issues addressed. It'd take an idiot to miss a problem in this area during a timing belt job.
If your problem is actually one of the chain tensioners in the head the shop can probably not be held responsible. A timing belt job does not address any issues with the chains and tensioners under the cam covers and these parts can indeed fail. However it should only damage one head and it should be possible to replace the head more cheaply than the entire engine.
-Joel.
12-17-2010, 09:05 AM
#7
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On the 32V engine my experience is that the chain starts to stretch, and especially on cold a loud clatter tikkery noise is present
and on extreme conditions i've had one where the chain had so much slack it was hitting the valvecover so much it went through!
The same happends to 40V engine where the chain and tensioner weares out.
Check out this pic it's from a 3.7 40V:
Uploaded with ImageShack.us
So if the chain can wearout so far that it can go through the valve cover i doubt your engine failure is because of that!
But still it is possible.
Check wich valves are bent, are the exhaustvalves and intakevalves bend its because the timingbelt was installed wrong or slipped!
Is it only the intakevalves that are bent it is probably because of the chain that went bust!
and on extreme conditions i've had one where the chain had so much slack it was hitting the valvecover so much it went through!
The same happends to 40V engine where the chain and tensioner weares out.
Check out this pic it's from a 3.7 40V:
Uploaded with ImageShack.us
So if the chain can wearout so far that it can go through the valve cover i doubt your engine failure is because of that!
But still it is possible.
Check wich valves are bent, are the exhaustvalves and intakevalves bend its because the timingbelt was installed wrong or slipped!
Is it only the intakevalves that are bent it is probably because of the chain that went bust!
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12-19-2010, 07:04 PM
#9
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Thanks for your advise.. The tech says he manually turned engine over before he started it up.. and they want to prove to me that the engine is still in time.. I asked another independent audi repair shop and one mechanic said couldn't happen and another older mechanic said that it was possible as he has seen it. The shop now wants to find a used good engine to put in this car as he says all the intake valves are bent and 2 of the cylinders show some scoring, one he says with some severty. The shop will not take full responsibily but wants to work with me to find a solution. This is still hard to believe that this could happen at this exact time. I may have to take legal action but I don't want to.
12-19-2010, 07:26 PM
#10
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The way I see it, you delivered a car running normally to them for scheduled maintenance...not a repair of a failing part...no evidence of a failing part when delivered. They performed the maintenance. Even if the billion to one worst case scenario happened as they said, it happened in their possession, with them operating it, after they did work involving the system that failed....tough luck...legally their fault.
I think you have a case that might interest a lawyer, unless they are willing to charge you no more than the original maintenance cost.
That's the chance they took. There was no analysis done in advance that indicated any possibility that, after they did the work, your car could fail. Botched job or bad luck doesn't matter...the damage was done in their possession, by them, no matter what caused it.
I think you have a case that might interest a lawyer, unless they are willing to charge you no more than the original maintenance cost.
That's the chance they took. There was no analysis done in advance that indicated any possibility that, after they did the work, your car could fail. Botched job or bad luck doesn't matter...the damage was done in their possession, by them, no matter what caused it.