Chain rattle worse on cold days
 

I have looked around the forum and can't find quite what I'm looking for.

I've had my 05 3.2 A6 for about a year and a half and it always had a very short chain rattle when I start it. I've read that this isn't really an issue when it only lasts a second. Lately, especially when it is cold out, I can hear the very loud rattle for a couple minutes, or else it goes away quicker if I start driving right away. Oil change history is good and I always use Mobil-1 0W-40.

I'm guessing cam tensioner isn't building pressure right away. Is it an issue I need to address right away?

If the chain rattle is lasting several minutes you should consider replacing the chain and tensioners ASAP.

Timing chain or cam chain? Car has 80k

Perhaps if you provided us with an audio clip the forum would be able to diagnosis what noise you are hearing. Right now we are rather limited on providing a diagnosis of the noise. Most of the chain noise at start up reported on the forum has been the timing chain.

Timing chain is the same thing as Cam chain. It's the chain that connects the crank case to cam shafts. Since we have 4 cams, the chain is rather complicated.

I really think the cam tensioners are Audi's Achilles heel. I have a 2009 3.0T engine with only 50K miles with the same issue. For now the noise only lasts about 3 seconds. I plan to get rid of the car if the noise starts to significantly last longer.

I have a second car so I don't drive the Audi everyday. What I normally do is start the car once a day, even on days I don't drive it, just to keep the oil pressure in the tensioner. I feel pretty stupid doing this on a car that was built only a few years ago but it definitely helps minimizing the frequency of the noise.

There are two things you have to watch out for if the rattling noise is lasting that long. One is that it could eventually break the chain guides and you will have to remove the engine to replace them. The other thing is that the chain will start to skip a tooth, or worse a few teeth. Since our engine is an interference engine, skipping more than a couple of teeth could deviate the timing enough to ruin your pistons and valves. The cost of rebuilding the engine would be prohibitive.

What's the worst thing about our engine is that the timing chain is located behind the engine. The parts don't cost whole lot but people report spending as much as $10K to have them replaced. If the chain is located on the front, I can't imagine costing more than $1K and I would do it as a preventive measure.

I love my Audi. This is my second C6 model. However, I feel that I can't keep the car as long as I would like because of issues like these. I just noticed that I have a very small leak at the radiator. Although the radiator only costs about $250, dealer quoted $600 in labor because you have to service the transmission. I live in Southern California so oxidation is not an issue. Kind a hard to believe I have to deal with a radiator issue on a relatively new car.

Unfortunately I don't plan on keeping the car more than a year.....

Just a correction/clarification. These engines are even more complicated than you think! There are 4 cams and 4 chains on the 3.2. One chain drives the oil pump and balance shaft. A second chain drives a pair of idler shafts which in turn drives two more chains, one for the left side cams and another for the right side cams. Each of these chains has a tensioner.

See page 20 in this link.

https://dl.dropboxusercontent.com/u/...n%20Drives.pdf

I think it is important to note that some people have 200+k on these engines with no problems with the timing chain and some are seeing problems at a little more than 100k miles. I think that the cars without problems are in the majority but that does not make it any less painful for those who have problems.

It appears that the chains themselves are not the problem, rather the it is the hard plastic tensioners which fail. Perhaps these should have been made of metal. I would agree that it would have been nice to have the timing chains in the front of the engine where they could be serviced if necessary. I am sure some engineer in Ingolstadt had a very good reason for this design. Personally, I think that every engineer should have to spend one month per year in the service bay to learn how to deal with their design decisions.

You just might be looking at chain replacement... Did that about a month and a half ago and its not pretty nor does your wallet walk away happily...
How cold is when your chain rattles for a couple minutes?

I finally got my first rattle today which lasted about 1 second before going away. But it was -2 or so and was parked at a slight incline with the engine facing downward if that makes any difference.. The 3.2 engine was definitely not designed to be started in subfreezing temps.

Timing chain tensioners and guides are likely going bad. I just had mine replaced after 6mons of doing what you say yours sounds like. One day when starting the car the timing jumped, that was when I limped it to the dealer only to be told it would cost me 11,000.00 to fix because they said if they do the job they would have to replace all 4 chains (which cost about 1,000.00 a piece). Their reasoning was warranty on the work done, it not policy to use old or possibly damaged parts.

Had a friend of a friend(who has done 17 repairs on the A6 C6 models with this issue)fix mine for 3,000.00. Chains very rarely need to be replaced, they don't stretch as much as some would say they do. He just did the guides and tensioners. The engine has to be pulled cause they are in back. When he got to my tensioners, they were so bad, they fell right off.

I'm just giving you my reality, I hope and pray yours is not the same.

Take care and best of luck to you