jjrichar

Just joined the forum. Great site. Lots of great information.

I have a problem with my car that if someone could help me with I'd be much appreciated. I've seached the forum for this issue and not found it. It's very different to the other common noises after start that I've seen mentioned.

When my car is started from cold, I get a quite loud grinding/rattling sound. It goes completely after about 2 seconds maximum. The colder the car is, and the longer between starts, the worse it is. If the car was going 30 minutes before, and then I start it, no noise. Note that I live in Australia, and the lowest temp the car would ever start at is about 5 deg C. It still does the same thing in Summer where the temp is obviously much higher than this.

I initially thought it was the hydraulic lifters, but it's not the tick, tick, tick sound that I would expect.

Also, I have the Bentley manual (software) and in the bulletins section it mentions that on some engines the variable valve mechanism can rattle significantly on startup, with no issues, and no fix available. It didn't mention my engine though (BAS) as one of the engines that this occurred on.

This has happened for a long time when starting the car (read years) with it only gradually getting worse over time.

Anyone have any ideas.

OGBULLYLOCDAWG

http://www.youtube.com/watch?v=UrYfW1-JA88

That noise?

I don't know what causes it (always assumed it was related to the cam chain tensioner), but my 2.8 (ATQ) does the same thing.

69gaugeman

This is caused by the cam chain tensioner. There is a check valve for the oil that is leaking in the head. Once it pressurizes it is fine.

itskoji

Do you know if there is a way to fix this? I have a 2001 a6 4.2l and i get this noise on cold start-ups and also sometimes when i accelerate from a stopped position at a light, etc.

MP4.2+6.0

I dealt with this on my old C4 A6 with the older 2V 2.8 motor. There was a TSB on it. The check valve was buried in the middle of the "V" of that motor. Once I got the manifold off and opened up the cover plate, access was easy. That's where the check valve was found on that motor. The check valve was available from the dealer as a piece part.

jjrichar

Guys, thanks for all the feedback.

Mine does sound like the video below, so I'm going to assume that's what it is.

Just for reference, I've attached the Technical Bulletin below for those who are interested. I haven't included the second page, but it says that there is no action required, and that changing any components will make no difference.

As you can see it doesn't include the 4.2L engine for the allroad.

The bulletin does list a number of engines for the A6, including a 4.2L V8. I've done a bit of reaseach in the Bentley software I have and all of these engines are a type where the camshaft timing is done by a toothed belt at the front of the engine, not numerous chains at the rear of the engine like the Allroad 4.2L. It's a completely different setup.



I'm still confused.

SloopJohnB@mac.com

The answer is that it's normal.

MP4.2+6.0

In the V under the upper block access cover. One for each cylinder head. Not the "for sure" fix, but if your problem has developed over time rather has always been there, a decent suspect. And since there are two, if you can isolate the noise to one sides/head or the other, even better. A few hours to R&I the manifold though, plus the check valve cost. Could also try engine flush just before an oil change, though I go sparingly w/ that if there is any question about seal integrity.