Help Please Rattle from rear of engine (B8 S4), what is it?

[Chris Paine]

I hope to be picking this car up over the weekend but when I went to view it, the engine had this rattle from the rear right hand side of the engine. The owner says it's an exhaust heat shield, does that sound right (excuse the pun)? This was started from cold and doesn't go away until the car is warmed up or revved harder than idle.

I know about the timing chain issues/rattles so that's my worry before completing the purchase basically.

 

[Tobe]

It's the upper chain tensioner/s, it's worth finding out when last oil change was, and what oil used. The right grade of oil and fresh can make this go away as it affects the oil pressure when cold. I say this as mine did this for a couple of months before an oil change completely cured it, changed to 0w40. Now only get a brief rattle if it's been sat for over a day.

If you do buy it I would factor in upper tensioner replacement at least just in case, but then get the oil changed straight away, and cross fingers.

 

[Chris Paine]

Thanks for the swift reply. The current owner is away on holiday at the moment but the car was serviced recently, like a couple of months ago. I don't have access to the invoice copy he has so can't recall what grade oil was used. I'm pretty sure it was just a standard oil service though.

Forgive me if this is a dumb question but I thought it was being caused by a timing chain/tensioner then the rattle would go away after a while? This stayed on for well over a minute. It was also definitely coming from more to the right hand side of the rear of the engine, which of course you can't hear on the video.

 

[Chris Paine]

Just showed the video to a mechanic friend of mine and he says "no way is that an exhaust heat shield". He reckons maybe a worn follower. Also I found in my pictures on my phone that I DID take a photo of the last service receipt and it was 5w30 oil used.

Anyone got any further thoughts? Thanks

 

[Tobe]

There's an upper tensioner on both sides behind the black cover. Mine did it on the left, and the right was silent. The vicious brief rattle is very well documented on the early models, and there's tsb's for it. After looking on other forums for ages there's only a few cases I've found where they have this problem as well, it's like a quieter rattle that gets louder over a few seconds then stops, then a few seconds later does the same, on mine it did exactly like it does in your video, sometimes wouldn't do it at all, and then other times when it did it it would last around a minute like you describe, it would carry on for a couple of times after the high idle after cold start.

I didn't really worry to much as when it's hot it's fine, and like i said changing the oil seems to have sorted it anyway. The tensioners are known to be dodgy on these and people who have had them replaced have reported that noises have come back. So for me I won't worry until something major goes obviously or a cat goes and I have to get the engine or box out anyway and then I'll do all the chains and tensioners at the same time. It would be good to test it once the engines warm/hot, turn it off and start it again after a couple of minutes or so, if you get any rattling at that point then it's a serious issue!

I understand the principle of how the tensioner works off oil pressure, but I don't really understand exactly how this noise works, as it seems to come and go, so whether it's related to oil pressure or just not enough oil reaching the chain drive? The brief loud rattle problem is just pressure where it drains out and has to come back upto pressure when started but this is different, I think if it was pressure related it should either rattle or not, and not come and go! I'd love to get an oil pressure gauge on one when it doing it and see if the oil pressure is actually fluctuating. All I know is oil fixed it! 0w40 is thinner when cold than 5w or 10w, so my theory is thinner oil means oil travels easier through the engine and pressure/flow get to the top of the engine quicker.

 

[Tobe]

Yeh I would say the owner knows exactly what it is and that's why it's for sale

 

[Chris Paine]

Many thanks for your help, it's genuinely much appreciated. The current owner of the car seems a very respectable guy so I doubt he's trying to stitch me up here. However I want to be very sure I'm not walking into big bills very soon into ownership. Annoyingly the whole gearbox was taken out and rebuilt 12k miles ago (at a cost of £3.4k) so I don't know why the chain/tensioners weren't done at the same time "if" they are a potential cause for concern on such a car. I know if I was having such a major job done I'd ask if any other preventative maintenance was worth doing at the same time. I have a copy of the invoice for that work and there's no mention of it being done.

 

[Chris Paine]

Forgot to ask earlier, what's the rough cost of an upper tensioner replacement? It may be that I have to factor this into the final agreed price on the car. I know it's a major job but I forgot to get a rough figure from my local indy specialist earlier.

 

[Tobe]

If you just want to do the upper tensioners, one side can be done with the engine still in the car, I forget which one it's tight but the sai valves(think that's what they are) behind the engine on each side have to come off to get the Chian covers off and one side won't be removable without taking the cat off which is a pain in itself.

If it's the right side that's easy and you are lucky and can do it that way then labour would be minimal. But if the engine has to come out get the whole lot done anyway while its out, all Chains tensioners and guides, as the extra for part and maybe another half hour while it's out will be worth it.

The ina upper tensioners are stupidly cheap on autodoc at the moment so maybe worth looking there for parts.

 

[Ginge247]

Forgot to ask earlier, what's the rough cost of an upper tensioner replacement? It may be that I have to factor this into the final agreed price on the car. I know it's a major job but I forgot to get a rough figure from my local indy specialist earlier.

If the noise has been happening for longer periods for some time the chain may need replacing now as well. Mine started rattling on start up for nearly a minute. Cost me nearly 3 grand for all the chains, tensioners and followers to be done. By the sound of that noise I wouldn't be running that chain with a tensioner.

Sent from my JSN-L21 using Tapatalk

 

[Dippy]

The vicious brief rattle is very well documented on the early models, and there's tsb's for it.

Indeed. And for those not aware, the revised version of this engine has redesigned timing chains. Audi wouldn't have done that without a reason.

 

[Chris Paine]

The car in question is an '09 model so I was aware that they're more prone to issues. Hence my growing caution. Can you take out a warranty to cover for such things? I image it would be pretty spendy if you could.

 

[AndrewW]

You can get used car warranties but they become very expensive for good cover (i remember an article a while back saying you're better off just putting the money you'd pay on a warranty into savings and have it on stand-by, obviously there will be exceptions)

They also don't technically cover issues which were present before the warranty started, whether they could prove this or not I don't know but something to consider.

My honest opinion would be give it a miss unless the price is really good and it's worth sorting the issue should it get any worse.

 

[Chris Paine]

The giving it a miss option is growing on me sadly. Price is a fiver under £10k. It's got 121k on the clock, 5 previous owners. Drives well and looks to be in reasonable condition, with the exception of that noise from the engine. It's stage 2 tuned by MRC - 3 years ago. I'm wondering if it's had a hard life even with a fsh.

Thanks for the continued help and support by the way. It's genuinely very much appreciated.

 

[Andy Butcher]

If it was my money I'd walk away.

 

[MattS5]

If it was my money I'd walk away.

Maybe even running away!! (how long has the current owner had it?)

 

[AndrewW]

Did you end up going for it @Chris Paine ?

 

[Chris Paine]

No in the end I bought another car, shown in the avatar. Very glad I did too as this was so much better than the other one.