Manifold Gasket Question.

richyb66 · #1 21st May 2012, 01:48 PM

Is there a gasket between the exhaust manifold and the cat downpipe in a 4.2 40v? It's in an S6 but I suppose all the 40v's are the same.

As one of my cats appears to gone (annoying rattle from inside), I've ordered a pair of new cats and I phoned Audi to order the gaskets. They seem to think there aren't any which I find hard to believe but not impossible. ELSAWIN doesn't seem to have an exploded view and I can't get on VAGCAT at the moment.

If this is the case, should I just use a like smear of assembly paste?

ainarssems · #2 21st May 2012, 03:04 PM

It's kind of conical, round (ball type if you wish) joint without gasket that allows slightly different angles and movement in joint sealing at the same time

richyb66 · #3 21st May 2012, 03:53 PM

Thanks for that, sounds like some manifolds I've seem before (SD1 Rover possibly?). A very light smear of paste won't hurt.

My new cats should arrive tomorrow, just need to sort out a pair of pre-cat lambda sensors and I'm all set for the weekend.

ainarssems · #4 21st May 2012, 04:17 PM

Quote:

Originally Posted by richyb66

Thanks for that, sounds like some manifolds I've seem before (SD1 Rover possibly?). A very light smear of paste won't hurt.

My new cats should arrive tomorrow, just need to sort out a pair of pre-cat lambda sensors and I'm all set for the weekend.

Be careful with paste some can damage cats and lambdas

richyb66 · #5 21st May 2012, 04:23 PM

I'll be sparing with it. What I'll probably do is loose fit everything so that the outlet of the down pipe is connected to the rest of the system and then loosen the connection at the manifold and apply a smear of paste before tightening it up.

If I go for lots of paste and leave the downpipe dangling or waggling around, some paste will no doubt drop down onto the cats.

daviesbike · #6 22nd May 2012, 11:11 AM

i would not bother with paste to be honest, the joints that ainarssems mentioned are expantion joints when fitted together and tightened up when the system gets hot it expands and creates a perfect seal and if you put any compound on there it might make the joint not seat correctly and might not seal when hot

just my 2 pence worth

ainarssems · #7 22nd May 2012, 01:04 PM

Quote:

If I go for lots of paste and leave the downpipe dangling or waggling around, some paste will no doubt drop down onto the cats.

It's not just about bits of paste falling in. The stuff that evaporates from paste can contaminate lambda and catalyst surfaces reducing efficiency or stop working altogether if using wrong paste. I avoid using any paste before or shortly after cats. I know any silicone sealant and coolant getting in exhaust will do that. Some exhaust pastes are OK to use but I avoid them just in case.

richyb66 · #8 22nd May 2012, 02:08 PM

New cats arrived this morning. The sealing face is indeed conical so if I can clean up the face on the manifold, I'll just bolt it together dry.

Lambda sensors for the downpipes were ordered today once I'd confirmed that the current ones were 4 wire. The downpipes look long (front to back) but not that high so it looks like I'll be able to get them out without having the front of the car too high off the ground.