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Chain flapping on a cold start is common on Audis and is caused by the tensioner not keeping oil pressure overnight. It's exacerbated by worn nylon shoes, such that the tensioner has to move a lot more to take up the slack. Not a big deal within reason, as long as it's only cold starts and a few clacks and the shoes are not worn out yet.
Actually, that is kind of a big deal. That initial start chain flapping not only wears out the chain, but the slapping chips pieces of the tensioner paddle guide away. Once all that material is gone, the chain makes metal to metal contact with the paddle itself.
The springs on the tensioner supply initial start up tension, then the hudtsilics take over once the pressure inside the tensioner builds up. The springs can weaken over time and if the tensioner isn't holding hydraulic pressure then the spring is trying to do all the tensioning work, which it can't. That chain in the earlier picture should be tight along that sprocket. I've never pulled a Cayenne tensioner, but the ones on my 997s of the same vintage are single piece assemblies and I imagine these should be too.
1. Change the timing chain tensioner.
2. Replace both the accessible upper chain guides
3. Retime your camshafts.
4. No need to replace the timing chain at this time.
1. Change the timing chain tensioner.
2. Replace both the accessible upper chain guides
3. Retime your camshafts.
4. No need to replace the timing chain at this time.
Thanks! I have a new tensioner on order and should have early this week. I checked the two upper chain guides and they show pretty minimal wear, so I’m thinking I will leave them at this point. The chain groove in them is probably less then the thickness of a piece of paper.
So $300 later I have my new tensioner. Definitely looks like it’s should be a one piece unit and not come apart in pieces like the old one. Spring does feel stronger on the new one. After installing, timing chain is still slack and after turning the engine over a few times by hand the chain is still popping off the camshaft actuator. I’m hoping it’s just because it not under any oil pressure still and it will firm up but again that could be wishful thinking and I could still be looking at a full chain replacement.
So $300 later I have my new tensioner. Definitely looks like it’s should be a one piece unit and not come apart in pieces like the old one. Spring does feel stronger on the new one. After installing, timing chain is still slack and after turning the engine over a few times by hand the chain is still popping off the camshaft actuator. I’m hoping it’s just because it not under any oil pressure still and it will firm up but again that could be wishful thinking and I could still be looking at a full chain replacement.
I'm afraid that is wishful thinking, IMHO. I suspect that the original tensioner pounded its way past the stop. In normal use, the tensioner should be compressed sufficiently such that it is never touching the stop. The fact that your tensioner was apparently extended to the stop indicates to me that there is something else amiss with your chain/guides (the latter seems most likely).
I'm afraid that is wishful thinking, IMHO. I suspect that the original tensioner pounded its way past the stop. In normal use, the tensioner should be compressed sufficiently such that it is never touching the stop. The fact that your tensioner was apparently extended to the stop indicates to me that there is something else amiss with your chain/guides (the latter seems most likely).
I agree with Brett on this. A brand new tensioner should supply enough static spring pressure without any oil pressure to keep the chain taut. The hydraulic aspect of the tensioner takes over when the engine is running to relieve the spring from doing the work all the time so spring is only during the work when the engine isn't actually running. The chain should be taut in it's static state. If it's not, either something else is amiss, like the chain has stretched or a guide that's not visible has worn to the point where the chain is able to take a straighter path than it should be able to, resulting in the slack.
I'm afraid that is wishful thinking, IMHO. I suspect that the original tensioner pounded its way past the stop. In normal use, the tensioner should be compressed sufficiently such that it is never touching the stop. The fact that your tensioner was apparently extended to the stop indicates to me that there is something else amiss with your chain/guides (the latter seems most likely).
This was certainly my concern as well. I had pretty much resigned myself to tearing it down for a chain replacement but thought I would try running it over a few times with the starter with the idea that maybe it would build some oil pressure in the tensioner. Surprisingly it seemed to actually work. Chain is now tight. Cranked it over a few more times by hand after and chain is still tight and is no longer popping off the cam adjuster. I’m going to reset the timing and put everything back together and cross my fingers.
When I had dubious cam readings I replaced the two cam adjust solenoids, timing chain tensioner, upper chain guides and also interchanged my intake cam phase adjusters between bank 1 & 2 whilst I had access.
I interchanged the phasers to monitor if the faulty cam readings transposed banks, then I would have a direction to troubleshoot.
Readjusted the cam timing and fortunately my cam readings were restored with nil faults evident after the above stated maintenance.
My timing chain on my 2003 Cayenne turbo has over 166,000 miles and my cam deviations now on both banks are well within the 5 degree limit. Both banks are each reading 0 +/- 1 degree.
This was certainly my concern as well. I had pretty much resigned myself to tearing it down for a chain replacement but thought I would try running it over a few times with the starter with the idea that maybe it would build some oil pressure in the tensioner. Surprisingly it seemed to actually work. Chain is now tight. Cranked it over a few more times by hand after and chain is still tight and is no longer popping off the cam adjuster. I’m going to reset the timing and put everything back together and cross my fingers.
It doesn't surprise me that the chain feels better now that the oil pressure is backing up the spring. But this doesn't change things IMO. Somehow the original tensioner was damaged. The only good explanation that I can come up with is that it was extended so far due to chain slack that it banged against its internal stop while the engine was running.
I can't blame you for wanting to try things out before diving into the front of the engine. Changing the timing components is a big job. I would suggest one thing to consider, that is to measure the distance between the surface where the tensioner seats against the block and where the end of the tensioner piston touches the back of the tensioning pad (inside the bore). I did a crude measurement on an engine I had here and estimated that the tensioner piston would be approximately half way compressed when installed. This was on a very high (270k) mile engine so it's probably an outside limit. I can get a better measurement for comparison if needed.
So I got everything back together today and fired it up. Idle is smoother then it’s ever been. After a good long drive no check engine light or codes. No misfires as per Durametric. I’m going to drive it this week and see if the problem returns but so far things are looking good. I was a little surprised to still be showing-9 cam deviation on both banks. When I set the timing, bank 1 was off by a fair bit bank 2 was spot on so I didn’t touch it. I was expecting cam deviation to improve.
Thanks everyone for all the feedback and advice! It was much appreciated!
Vehicle continues to run well. Good idle, no misfires or CEL. Cam deviation is unchanged at -9 on both banks which surprised me. When I set the timing, bank one was out but bank two was spot on, so I didn’t touch it. I would have thought I would at least have seen some change in cam deviation on bank one after adjusting the cam shafts. Regardless, I’m obviously happy I didn’t need a new engine as suggested by the shop when I took it in. I could have been out several thousand dollars if I didn’t investigate further.
Good to see the engine is running well and that the workshop didn’t get to milk your wallet.
Did you happen to data log any “actual cam angle” readings at various engine speeds to confirm the cam adjusting components are working?
I did check actual cam angles sitting in the driveway. Bank one sits pretty much at zero at idle. Bank two tends to fluctuate +/- 1 degree. With an increase in engine speed you can see the cam angles adjusting. I should take a better look under actual driving conditions.
06-18-2021, 09:18 AM
