jerry-lincoln-ne

I have a similar problem. The dealer is getting some guidance from Audi. Not sure why that is necessary. But, this dealership does very good work.

This is covered by my extended warranty. However, I'm curious what this work costs. Seems like many labor hours plus parts (e.g., a new chain).

odoboyusa

It looks like this thread grew a bit since I last looked. I started it and now I found the issue: a broken timing guide on the middle chain, the one upstream from the crankshaft. Since the guide broke in two it collapsed and that throws the valve timing off and everything else. The odd part is that i have another exact same type engine and it has the same guide broken. Seems like a design issue. Also, in the following pics you can see the difference between the old and new guide.

Here's the culprit, the old one and new one:
<img src="https://forums.audiworld.com/picture.php?albumid=166213&pictureid=235824">

Then here's the broken guide before I took it out of the engine. Doesn't look like a big crack but it creates about 5mm more in sideways chain slack. Enough to screw things up.



Here's the interesting part, the old guide seems to be a bit different than the new one:

<img src="https://forums.audiworld.com/picture.php?albumid=166213&pictureid=235825">

And for those that have not yet seen the whole "engineering marvel" setup, here it is. I still maintain that the design is flawed, too many things to go wrong which is the opposite intent for a timing chain. Seems like this broken guide was an after-thought, they had to make that cut on the back of it and that's where it breaks.

<img src="https://forums.audiworld.com/picture.php?albumid=166213&pictureid=235822">

jujuC6

Thanx for the detailed pics and info odoboyusa, I think my problem was the upper right guide. So is it a matter of time before the other guides start breaking too?. The new guide appears to be a different material and hopefully it is much stronger.

BOsA6

It sure is a design flaw... same guide broke on my 05 A6 4.2. I ended up replacing all guides,tentioners,cam adjusters and chains! Don't ever want to remove this engine again.(100000miles)

odoboyusa

The new guide is of the same material as the old one, PA66. it's a nylon as far as I know but I think there are stronger similar materials but I know these guides need to compromise on friction.

Another messed up thing on the same note is that 3 out of 4 chain tensioners were leaking oil - the power take-off one seemed fine. This was just by spinning the engine by hand a couple times. Now I understand where the startup noise was coming from. A different kind of oil might fix it temporarily (like others said) but it will come back.

I started a different thread looking for suggestions on supporting these guides. I also have a couple ideas but I'll do a bit of research and if my final idea looks doable I'll share it with the great folks of this forum.

odoboyusa

Finished the project about two months ago and everything seems fine. Engine is more powerful, more responsive and gas mileage went up by about 3-4 mpg.

I'd like to make a correction, the tensioners were not leaking oil, they have a small hole at the end of the piston to probably push air out and probably get oil in the chains area.

If you're doing this job, get the proper silicone as most parts in the back get sealed by silicone only, no gaskets.

At this point, the car is awesome, no complaints. The existing chains were not stretched at all but since I had new ones, I replaced them. The whole problem was caused by the broken guide.

I do understand why the system was put in the rear... to save space.. but serviceability was the one to suffer.

Hope this information helps others.
PM me if you need any advice.

jujuC6

Hi everyone, a year ago around Christmas I had this chain rattling problem which the indy shop I took my car to was able to fix without removing my engine. Sorry for not updating this post after resolving my issue. A year later (now) my problem has returned but this time as a more subtle diesel engine like sound compared to last time. I listened with a car stethoscope and determined that the sound was originating from the passenger side cam tensioner. This is the same tensioner my indi shop replaced last year. I brought the car back to them and they confirmed that the passenger side cam tesioner they replaced had failed again. They took it out today and told me that for some reason the tensioner has become lazy and does not want to open all the way. To my luck which does not happen often enough the indy shop warranties their work for 36months and I am covered. Just wanted to share the bad and good news.

z06bigbird

Timing chains do stretch. Jackrabbit starts will do cause the chain to stretch as will "goosing the engine" on a regular basis.

Additionally, manufacturers of timing chains have been partially responsible for stretched chains. GM purchased a ton of timing chains for their 3.6 engines in the 2007 or 2008 CTS. Covered under warranty. Replacement chains had the same problem until manufacturer changed the product.

Later years of the CTS did not have this problem. Cadillac DTS (northstar) has not had a timing chain problem. I wonder how their timing chain guides compare to Audi's.

raj99

I just checked the measurement block 093 and mine read -4kw on both bank 1 & 2. is this something I should worry about? it read this while the car was running as well when the ignition was on, not running.

odoboyusa

those values are only calculated on engine start when the crankshaft syncs with the camshafts so as far as i know they don't change often at runtime.

Your values look OK, I think -7 is the service limit.

One simple test even without vag-com is to very slowly accelerate the engine from idle up to about 2500rpm and look for rpms at which you hear a knock, usually from the driver side head, towards the firewall. In my case the knock was around 1800rpm and very easily repeatable. On the v8 it's "normal" for the engine to vibrate at certain rpms, supposedly has to do with harmonics and stuff. vibrations are ok, knocking not so.

In retrospective and after dealing with several more engines with the timing chains (4.2 v8 and 3.2 v6) I noticed bad engine oil quality causes significant wear (grooves) in the chain guides. What I'm trying to say is that it's really not worth using the cheapest oil or going over the service interval.

Honestly I really wish the timing system and the camshaft tensioners would use a completely different oil supply rather than using the engine oil but cost would go up significantly.