Hi people,

For ages now, well since I had a new cat fitted over a year ago, the manifold to down pipe flange has been leaking. This manifests itself as an annoying rasp/ tinny rattle at anything other than light throttle openings. If you put your hand near the joint, you can feel it blowing against your hand.

I've since replaced the metal gasket that's sandwiched in there, but it only made it 10% better, so hardly any noticeable difference.

So, what’s best to do with it?

Putting exhaust paste around the outside wouldn’t do anything would it, it'd just drop off/ blow off, in a handful of miles? Normally, you'd apply some paste on the face of the flange, but you can't do this, as the majority of exhaust pastes contain silicone which spikes the cat and lambda. Does anyone know of any silicone free exhaust paste (which wouldn't almost permanently weld the two pieces together)?

My dad had suggest using a relatively thicker copper gasket instead of the steel one, as when hot, the copper can be compressed, thus sealing up any leaks.

What do you reckon?

i reckon you should go get a new manifold from a scrap yard it will cost you next to nothing and it will mean you can clean the mating surface really well, put a new gasket on again and some fresh bolts.

i reckon i could get a manifold if i wanted for one of your cars for about 10 quid max around mine if i had time. a gasket is a couple of quid. job done!

like youve said really. fucking on with paste is gonna last a few miles max. maybe the surfaces are warped slightly????

Cheers Dan,

I think the manifold is fine, its the new down pipe where I’m pointing the finger. When I removed the old gasket, you could see where it was leaking, similarly you can see it on the photo below (look right at the very top). If you were to look at the mating surface on the manifold, there are no such marks.

I'm thinking on the same lines as you, that the face of the flange on the down pipe is warped (manufacturing fault most probably). Ideally, I'd remove the whole section, and file the face flat. But removing this section is a right pain, so I only want to do it once, preferably leaving the pipe attached to the car.

try a gasket from a different supplier

i got one from Andrew Pages and it was blowing.......tried some exhaust paste on it & it still leaked

so.....i got another gasket thats a lot better quality & thicker from Waterloo and its been fine, does'nt blow at all

Paul

Thanks for that. I was thinking about a VW one (only a fiver). Do you think a copper one would work?

Come one Dan, VAG ALL THE WAY BABY

Oh.. and get some fuel treatment while you're at it!

On a more serious note - I'd get a vag gasket, clean and lightly sand the mating surfaces.

I've got a spare downpipe/ manifold if you need one Are the studs that attach them together ok and torque up alright?

Might even be worth seeing if you can get the face skimmed.

Come one Dan, VAG ALL THE WAY BABY

Oh.. and get some fuel treatment while you're at it!

On a more serious note - I'd get a vag gasket, clean and lightly sand the mating surfaces.

I've got a spare downpipe/ manifold if you need one Are the studs that attach them together ok and torque up alright?

Actually, I need some fuel treatment, now you mention it.

Yeah, I might clean and sand the surfaces, was just a bit concerned about any metal filings going down into the catalyst. With regards to the bolts, now that you mention it, these were all a bit tired and a proper bugger to shift. They're tightened to a very high torque though, but could probably do with replacing anyway. Thanks for the offer on the spare manifold, much appreciated , but I think mines OK.

Might even be worth seeing if you can get the face skimmed

Yeah, maybe, but I’ll leave that until later because logistically, I think it'd be a bit awkward.

UPDATE:- Finally got around to doing this!

Last week, we removed the down pipe (along with the whole exhaust system, as this was actually easier than removing just the front section) and had a good look at what's going on. I put a metal ruler on the face of the flange....and it's quite warped to say the least. I filed the face and took as much of the high points off as I could, which took ages, and put all back complete with a new gasket.

Started up and the noise was still there It's still quite bad when cold, but there's a marked improvement once it's warmed up and everything’s' expanded to make up the gaps.

A noteworthy point was, the order in which the bolts were tightened seemed to make quite a difference. I slackened and then re-tightened the bolts in a different order, starting with the ones which nearest the leak, and this seemed to help it seal better. I'm not finished with it yet. When I can be bothered, i'll take it off again and try to make the flange as flat as possible and put the exhaust back one piece at a time, as I think the rest of the system may have been preventing the flange lining up properly.