D2 S8 - Big end gone?

[RICKY D]

Evening guys,

Just popped out to the shops and as I was heading back I opened the window because I thought I heard a rattling around. I nearly cried when I heard what sounds like the big end rattling away. It seems to increase and get louder with revs from what I can hear but the car doesn't seem to vibrate or be down on power.

I know this is difficult to diagnose without a video, but I'm not going to sleep tonight if I think its kaput! Its very cold and dark here but I had a real quick listen under the car and if anything it sounds like its coming from the behind the engine, more towards where the exhaust joins from the two banks to one.

Is there any chance others have had this and it turned out to be something simple like an exhaust clamp maybe?

Any help appreciated.

Cheers
Rich

[HPsauce]

More likely one of the catalysts, they can make a hell of a racket!

[RICKY D]

Really? Could it be the internals breaking up then? It sounds terrible - really like the engine is on its way out.

[RICKY D]

You've both given me some comfort for now - thanks!

It's definitely not the tensioners. I hear them briefly on start up on cold morning and they sound different. They are on my long term list of things to replace as my mileage is just over 130k now.

[MikkiJayne]

Yeah the cats are a known problem. A forum member recently sent theirs to Germany to have new insides fitted. Can't remember who though, but there is a thread about it. Not cheap, but less than brand new ones!

Are you familiar with the concept of a 'listening stick'? Get a large screwdriver and stick the handle end to your ear, and then poke the other end around the engine. It works like a stethoscope and amplifies the sounds in the area in which it is poked. Its very easy to hear valvetrain noise like that (ie the cam tensioners). You'll hear straight away if its big ends that way too - touch it on the block where the engine number is at the front.

Edit - I'm taking far too long typing replies tonight

[HPsauce]

My nearside Cat was failing when I bought the car, factored into the price.
It never failed an MOT but I replaced it eventually, by which time there was just one medium lump of ceramic substrate rattling around inside, making a very loud noise but doing nothing.
The rest had blown out the back as powder

Get a skilled mechanic to have a listen , they'll soon tell you what it is.

Adrian_E had his cats done in Germany, then sold his FE!

[Adrian E]

Yep, was me that had cats refurbished. Much cheaper long term than replacing one from Audi (Audi price is £950ish EACH!)

There's a thread on here with the details IF it turns out to be that

[Goran]

My cats were rattling terribly just last year, sounded really awful and loud. When I had them removed for new ones I could see why, one huge chunk was lose and rattling away. The noise varied with revs.
Get under there with the engine running maybe you will be able to locate the noise as the cats. If you really want to make sure disconnect the cats, although that would be a pain to do as the drivers side cat is welded to the downpipe. Thanks Audi for another helpful design 'feature'
The stock ones are made using ceramic honeycomb, not very durable.

[briang9]

Originally Posted by HPsauce

More likely one of the catalysts, they can make a hell of a racket!

yes I agree, I thought same as you when mine went, can be very loud and does increase with extra throttle, you can get non Audi cats for a fraction of the cost of OEM, however as above they can throw the EML, I just bought a simple code reader from ebay for around a fiver which cancels it. You could get the sensors coded out but at the £350 I was quoted it's not worth it IMHO.. hope its not too expensive for you

[RICKY D]

Thanks for all of the encouraging words guys, it's been appreciated while I've been worrying about it for the past few days.

I got the beast on the ramp today and had a good look with my mechanic. He immediately said its one of your cats breaking up internally (offside one) but he could understand why I thought it was the bottom end knock from outside the car. Underneath it's much easier to see/hear it's one of the cats.

I feel a little silly for panicking now

Thanks to you guys who pretty much diagnosed this well in advance, I was at least able to get some sleep the past few nights

Thank you all ( one relieved S owner)

I have no EML on at the moment but as more breaks up will this trigger it? Thinking long term I guess I will need to replace it. Adrian I will have a search for your thread as that sound like a good compromise. As much as I like OE parts; £950 each