S6 Rattle - timing chain going?

A6 All/ S6 All
#1

I’m not having much luck with my S6. I’ve just sorted (fingers crossed) a load of issues with oil leaks and the crankcase breather system. My mechanic has pointed out that the rattle on start-up that lasts about 30 seconds may be my timing chain.

The rattle does sound to come from the engine bay - as you look to the front of the car its on the right underneath the windscreen wipers. I’ve researched it but have a couple of questions.

Is this something I need to do sooner rather than later, or just deal with it if it gets worse? Since the chains rarely fail is it most likely to be a failing guide, ie easy job to sort once the engines out? I’m just trying to prepare myself for what I have in store…

#2

How many miles? I haven’t heard of premature failures of the timing chain on the c6 s6. It’s possible though. What does your mechanic recommend to do?

#3

Just short of 100k miles. He said it sounds like the chain maybe dries out and after 20s or so of revolving it has time to get lubricated so the rattle stops.

Taking out the engine isn’t a major problem, it just seems an overreaction if a short rattle is the only issue. I don’t know how much a timing kit would be though.

#4

I’ve just had a close listen to the engine on start-up and it does seem to rattle or run rough for 1 minute before going smooth. I personally don’t think it’s a rattle from the area of the timing chain, sounds more like the intake manifold. We had that off the other day and opened it up and all seems in order so not sure what the sound is. I’ll try to record it but doubt it will translate well to video; car noises never do.

#5

Chain rattle usually wont last that long. I dont think its going to be that. I think the V10 motors have the updated guides and use the same sprockets like the S5 and they hold up really well.

When did this start. Did this just start after you had the intake manifold off.

#6

It’s done it ever since I’ve had the car, and is no different after removing the intake manifold. It sounds like a piece of plastic is loose somewhere, but this wouldn’t stop after a minute. It does make sense that it would be something that is deprived of oil for a minute initially but gets lubed up within a minute.

I think the guy who sold me the car knew full well about the oil leak; part of my suspicion was he put in excess oil and used 10w 40 (thicker to stop it leaking as much). I’m wondering if I should get it changed to recommended spec.

#7

See if you can get a video. The fact that it lasts that long makes me think its not oil related. If you shut the car off and start it again will it do the same thing. How long after you shut off the car until it comes back. Also is it exactly a minute long. try to time it if you can. Also try starting the car and if it rattles turn off the car and start it again a few seconds later see if that has any effect.

The thicker oil isnt bad in the hotter months.

#8

I tried to do a video this morning but it was neither use nor ornament. I’ll try again in better light.

The rattle lasts one minute, and the whole engine seems to get smoother when it stops. However it started earlier, I stopped the engine after a couple of seconds and restarted and the noise was not there.

It’s difficult to diagnose as the noise doesn’t last long, and then you have to leave the car around 8 hours before it does it again. I’ll aim to get a video soon and post the link up.

#9

I wonder if it could be something in the SAI system?

Does it happen on every start or is a cold or warm only start issue?

#10

It has been happening on every start when the car has been left about 8 hours. I went to film it this morning and there was no noise at all. It’s typical when diagnosing things from noises!!!

If something goes wrong it’s no big problem, I just don’t want my timing to go and smash the engine up. Anything else if probably not a big issue. I’ll mention the SAI to the mechanic when I go back for a check up next week.

Does anyone else have a rougher engine for a minute on startup before it settles down?

#11

Do you have a Milltek exhaust by any chance?

My S6 has similar symptoms. It seems to happen whenever the engine is cold, and goes away once it’s warm. Anything over about 3k RPM I hear (what sounds to me like) an exhaust system rattle. I had assumed there was something loose in my exhaust, but thermal expansion causes it to go away after a while. I have not yet identified the exact source of the sound.

#12

It’s not really rough, as in shaky, but it can by a little “jumpy” for the 10 or 20 seconds after a cold startup. If I put the car in Drive or Reverse immediately after starting the engine cold, the car will feel lurchy. During that time, and then for another 40 seconds or so after that, the exhaust is much louder than normal and the idle is about 1k rpm. After 60 seconds of that, everything calms back down to normal (Some believe the ECU does this intentionally to warm up the exhaust system), although the rattle I described earlier could remain for up to another 2 or 3 minutes.

#13

What your mentioning is the SAI system. The ECU is allowing the SAI system to push extra air into the exhaust to warm up the cats so they get up to operational temp quicker. The SAI system only works for the first min or so. It will make for a louder cold start and rough conditions until it turns off

#14

Mine does the EXACT same thing. Thought it could be a slight miss when cold due to carbon buildup or something. Been looking into options for carbon clean.

#15

Excellent. The rattle does sound like it’s from the exhaust area, but it depends on where you are stood in relation to the car. I’m satisfied it’s not the timing chain now after listening carefully to some cold starts. I didn’t even know about the SAI system; the same way I never knew cars had crankcase breather systems until I got the S6 (and it failed).

Thanks for this guys, let’s me enjoy the car without worrying about start-up noises.

#16

There’s really only one option for the carbon clean as far as I can tell. I can’t imagine there are any realistic shortcuts to removing the manifold and getting scrubbing. Just did mine however and it makes no difference to the 60 second rough / lumpy startup.

#17

carbon is only removed by getting in there and taking it off. To do that correctly you need to pull the intake manifold.

#18

I’ve got the same problem–especially if I haven’t driven the car for weeks. (115K miles)

But I’d like to know if it’s just an oil circulation issue, or a reason to take the engine out and do a timing chain service. (My mechanic thinks my oil leak is coming from the cam gaskets, but he can’t be sure unless he takes the engine out.)

I haven’t found any video to hear what chain rattle is supposed to sound like. But here’s a video of mine at startup:

Lets play "Fix it or Scrap it"
#19

Slightly hard to tell from that. But to me it sounds like it’s not rattle.

A few things to keep in mind. If you let the motor sit long enough the lifters can bleed down. There is a chunk of time where there is no oil so that can also cause ticking.

#20

I think that probably the case because once the oil starts to flow the engine seems to run smoothly. But I’d still like to know about timing chain rattle. The car is 13y old @ 115K miles. If I’m going to have to take the engine out, I’d rather do it now when the labor cost is a fraction of my next post.

Has anyone found a video that demonstrates what it sounds like when your timing chain is about to go off the rails?