Grinding noise on start. AR 4.2L
12-16-2011, 03:45 AM
#1
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Grinding noise on start. AR 4.2L
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.
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.
12-16-2011, 06:25 AM
#2
AudiWorld Member
I think my car does the same thing, although I consider it more of a rattle than grinding noise. I might try and get a video clip of it sometime. My theory is that it comes from the timing chain. As the car sits the oil runs down to the bottom. When you start it, it takes a few seconds for the oil to pump throughout the system again, leaving the chains to rattle on the guides while this is happening. But this is only my theory so it could be wrong. You might try searching the B6 S4 forum as well since they have the same engine.
12-16-2011, 07:23 AM
#3
AudiWorld Member
Thinking about this more, I searched the S4 forums a bit and found this:
It seems to be common, but not really a problem and no way to fix it. I agree it does sound bad though.
full thread here: https://www.audiworld.com/forums/sho...t=rattle+start
TSB 2010294/4
Rattle/knocking noise from camshaft adjuster at engine start
Condition
Rattle or knocking noise from camshaft chain tensioner(s) or camshaft adjuster(s) for 1-2 seconds after engine start.
Technical Background
The camshaft adjustment is hydraulically actuated and controlled by the engine oil pressure. If the engine has been turned off for a long time, the oil pressure drops down and the oil partially flows back into the oil sump.
To ensure an efficient camshaft adjustment right after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as fast as possible. During this time, a rattle or knocking noise may be noticeable.
This noise is normal at engine start and will last until the oil pressure is fully built up, which takes about 1-2 seconds.
Service
Do not replace the Camshaft Tensioner(s) or Camshaft Adjuster(s) for a noise concern as described above.
Replacing the Camshaft Tensioner(s) or Camshaft Adjuster(s) will not eliminate this noise.
Rattle/knocking noise from camshaft adjuster at engine start
Condition
Rattle or knocking noise from camshaft chain tensioner(s) or camshaft adjuster(s) for 1-2 seconds after engine start.
Technical Background
The camshaft adjustment is hydraulically actuated and controlled by the engine oil pressure. If the engine has been turned off for a long time, the oil pressure drops down and the oil partially flows back into the oil sump.
To ensure an efficient camshaft adjustment right after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as fast as possible. During this time, a rattle or knocking noise may be noticeable.
This noise is normal at engine start and will last until the oil pressure is fully built up, which takes about 1-2 seconds.
Service
Do not replace the Camshaft Tensioner(s) or Camshaft Adjuster(s) for a noise concern as described above.
Replacing the Camshaft Tensioner(s) or Camshaft Adjuster(s) will not eliminate this noise.
full thread here: https://www.audiworld.com/forums/sho...t=rattle+start
12-16-2011, 08:48 AM
#4
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Got the same issue on mine, make sure to use a quality oil and change more frequently as suggested in that thread, my chain rattle seemed to be reduced after doing that.
I change it about every 3k miles or 5000kms.
Any fixes would cost thousands of dollars as the whole engine needs to be dropped in order to be serviced.
I change it about every 3k miles or 5000kms.
Any fixes would cost thousands of dollars as the whole engine needs to be dropped in order to be serviced.
12-16-2011, 02:41 PM
#5
AudiWorld Member
Does it sound like this?
http://www.youtube.com/watch?v=xAR4CeXjDTg
That is pretty much what mine does too.
I don't see why changing the oil more often would make much of a difference, other than fresh oil might flow better or stay in the chain tensioners better? I've been sticking with the Audi 10k oil change interval so far on my car, although most S4 people are changing their oil about every 5k miles since they seem more worried about engine issues. I've been considering going to 5k intervals, but definitely not 3k with how much oil this car holds.
http://www.youtube.com/watch?v=xAR4CeXjDTg
That is pretty much what mine does too.
I don't see why changing the oil more often would make much of a difference, other than fresh oil might flow better or stay in the chain tensioners better? I've been sticking with the Audi 10k oil change interval so far on my car, although most S4 people are changing their oil about every 5k miles since they seem more worried about engine issues. I've been considering going to 5k intervals, but definitely not 3k with how much oil this car holds.
12-16-2011, 04:17 PM
#6
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Mine also makes the same noise on start up, on the odd occasion it will not do it but it certainly seems to do it more now the mornings are a little colder..
I'm glad i found this thread as it now puts my mind at ease... i has initially thought it was a loose baffle in the exhaust as my old V6 Passat used to have that problem.
I'm glad i found this thread as it now puts my mind at ease... i has initially thought it was a loose baffle in the exhaust as my old V6 Passat used to have that problem.
12-17-2011, 06:28 AM
#7
AudiWorld Member
The sound reminds me of when the air conditioning failed on mine. The gears stripped on the shaft and inside the chain housing. It was an expensive repair.
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12-17-2011, 11:52 AM
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12-17-2011, 06:58 PM
#9
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The AC shaft develops issues.....
https://www.audiworld.com/forums/sho...php?p=24042639
http://forums.quattroworld.com/allroad/msgs/11130.phtml
Search for posts by MYD-WGN about the shaft
https://www.audiworld.com/forums/sho...php?p=24042639
http://forums.quattroworld.com/allroad/msgs/11130.phtml
Search for posts by MYD-WGN about the shaft
12-18-2011, 08:22 AM
#10
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Technical Bulletin attached
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
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
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