2004 V8 Engine failure. Skipped *chain* timing after *belt* job. Please advise! - Club Touareg Forums
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post #1 of 24 Old 03-19-2015 Thread Starter
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2004 V8 Engine failure. Skipped *chain* timing after *belt* job. Please advise!

Need some input on this issue.

Appreciate your help in taking the time to read.

2004 V8 bought several months ago with ~100k miles...usual issues initially, such as dead diaphragms on the intake, stuck plastic arms, vacuum leak from same general location. Chain rattle for 2 sec upon cold start, which seems to be the common issue and even described as normal in the TSB, as the owners know. That's why I didn't worry about it too much. Slight lifter noise/tick which also seemed not a big deal for the mileage.

Changed oil and air filters, drove the car as is for at least a months, with some harder driving when needed on the tough NYC roads. No issues with the pull or the drive characteristics.
Finally got to the timing belt job which was done by the trusted shop with a relationship over 7 years with all my cars. The guy doing the job is a very knowledgeable mechanic with deep knowledge of the european cars. Changed the plugs along with the timing belt to Denso NKGs.

Picked up a car after the work, and the engine was smoother than before at idle, felt great, just purring , with same 2 sec chain noise upon cold start. Drove the car home for about 15 miles both street and hwy...everything felt great and smooth. Parked overnight.

Woke up started the car and it immediately started idling very rough with the check engine flashing, then after a minute it stopped flashing and the roughness got slightly better...shaked like a diesel with loud lifter noise.
Drove it to the mechanic staying under 1.5k RPM, since the CEL wasn't flashing any longer. Hoped to place blame at the plugs.

Diagnosis:
Misfires on left bank. Driver side chain slipped a tooth in timing. With valve cover open, the tensioner plastic guide is disintegrated. Left side of the engine is not holding compression with camshafts at TDC. Currently taking off the cylinder block to see if there's any damage to the cylinders/rods which would basically qualify for an engine replacement.


Now the question of the day.
Is this just a crazy coincidence and awful timing(pun intended), or could the timing belt job somehow affect the catastrophic failure on the driver bank leading to the timing skip? I am not THAT mechanically knowledgeable to make accurate assumptions, except that some tighter tolerances, less slack or some kind of a seal damage that resulted in the failure. Obviously the shop states there is no direct connection to the timing belt job, but I wanted to get some second opinion on this.

If you read all the way through, I certainly appreciate it, as well as any input you may provide.
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post #2 of 24 Old 03-19-2015
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As your V8 has a timing belt and not a chain, I'm confused by references to a chain.
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post #3 of 24 Old 03-19-2015
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Which parts were replaced and which parts were NOT replaced as part of the timing belt job?

Did you buy the parts or did the mechanic source the parts?

The reason I ask is there are a few possible failure points :

1. Engine was not timed properly when belt was reinstalled
2. Loss of tension in the system
3. Broken tooth on belt

Obviously part of putting a new timing belt on involves checking timing, tension, etc.

If you have known the mechanic for 7+ years I think you are entitled to ask some HARD questions.
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post #4 of 24 Old 03-19-2015 Thread Starter
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Quote:
Originally Posted by noobytoogy View Post
As your V8 has a timing belt and not a chain, I'm confused by references to a chain.
Timing belt VS Camshaft chain in overhead Cylinder head.
00 2000 Audi A6 C5 4 2 Driver Side Engine Cylinder Head | eBay
Picture shows the chain on the right(engine front), where the tensioner in the middle controls the slack in the chain.
The exaust camshaft went out of alignment with the intake camshaft by one tooth of the gear.

Quote:
Originally Posted by benb2376 View Post
Which parts were replaced and which parts were NOT replaced as part of the timing belt job?

Did you buy the parts or did the mechanic source the parts?

The reason I ask is there are a few possible failure points :

1. Engine was not timed properly when belt was reinstalled
2. Loss of tension in the system
3. Broken tooth on belt

Obviously part of putting a new timing belt on involves checking timing, tension, etc.

If you have known the mechanic for 7+ years I think you are entitled to ask some HARD questions.
Timing belt kit with water pump from Gates, Behr thermostat, accessory belt Gates, spark plugs Denso NGK.

All parts sourced and brought in by me.

1.Timing was done correctly I assume, as the tech did check the timing through the computer after completion. In addition the engine worked perfectly fine and noticeably smoother than before (or so it seemed). The skip in timing happened I am guessing on startup the next morning, as it couldn't have happened overnight with the engine off, and it worked great with no CEL the previous day up to being turned off.

2.Loss of tension in the camshaft chain in the cylinder head is obvious, as the plastic guide of the tensioner is gone, but was it that way for a long time before or not no one knows. The issue is why did it decide to disintegrate all of a sudden and did it work fine in the same condition(no plastic guide) all this time prior to the timing belt job.

3.I assume that he had enough experience to check the brand new parts for the possible defects, which are unlikely in themselves.

Please help me find a connection between doing the timing belt job and the camshaft chain skipping a tooth the next day. Why didn't it happen right away or before getting home?
Oil level/pressure?
Accessory belt connection?
Where is the cam position sensor's role in all this?
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post #5 of 24 Old 05-30-2015
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Any updates on this?
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post #6 of 24 Old 05-30-2015
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If you read thru the v6 timing chain problems, the V6 have the same plastic guide and it fails all the time. If I have to hazard a guess, the plastic guide was about to fail no matter what was or was not done. Would also appreciate an update.
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post #7 of 24 Old 05-30-2015
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This should help explain the problem to everyone. It has lots of good pictures.

Replacing cam chain tensioner and/or pads on bank #1 of 40V motor
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post #8 of 24 Old 05-31-2015 Thread Starter
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Driver side cylinder head replaced with a used similar mileage assembly. Both tensioners and their chains replaced with German aftermarket units as the oem cost is unjustifiable. Full gasket job done and repaired the intake vacuum pumps while at it. New coils and battery added.
Issues encountered:
A loud whistle from the air intake, which turned out to be a leak in the middle, where the gasket set from reinz wasn't sealing properly. Most likely to a slight misalignment due to the new cylinder head which I don't know the story from. An oem intake gasket set with additional silicone for impact got rid of the leak.

Timing between the belt and the cams as well as the chain timing on each cylinder head was done around three times, as the mechanical timing looked spot on, while the passenger bank showed camshaft codes and idled a bit rough. In the end the cam timing was movedover by a tooth and the engine worked smooth as silk. They said it was neither intuitive nor proper per the markings but it worked.

Remained with the issue of MIL on with the camshaft intermittent signal codes. Played around with camshaft sensors and in the process of elimination and checking the magnets inside the heads, the senior mechanic meditated on it for a week and got the answer from the ether, that it most likely is due to the tensioners, as the sensors only throw codes after about 3000 rpm. I decided it was fair game as is and not an issue for me.

No pressure codes or issues. No misfires. Absolutely no chain sounds from a cold start! I would seriously advise anyone like me who checked all the TSBs etc where it is noted by VW as normal, to open the heads up and check everything. My engine works smooth and quiet and I am assuming the corporate just avoided doing an expensive recall on all these engines. When I had failure on that faithful day, the exhaust camshaft skipped by 60 degrees. That is a catastrophic failure and you shouldn't operate as I did, but no further damage except for marks on the short block pistons.
Oh and the ticking that I had which sounded like lifter noise at low rpm is no more.

Was that a detailed enough follow up?
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post #9 of 24 Old 05-31-2015
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thank you very much for the detailed answer
and could you share the link or the brand of the chain tensioners you bought? thank you
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post #10 of 24 Old 05-31-2015 Thread Starter
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eBay seller deutschepartsusa. Current listing shows manufacturer as OEMQ, but I think it was different one when I bought. Best to inquire directly with the seller.
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