1850 manifold to downpipe. How to seal?

[cliftyhanger]

Had a couple of goes so far, the second one was way better as the system seemed to have settled and lost any tension. But is there a definitive method of getting it to seal? Before I crawl under there at the weekend, I would like to know the secret if it exists! or is it just down to a decent sealant?
TIA

[sprint95m]

That is a good question Clive!


Some (or a lot of new?) cars have a flexible gasket seal between the exhaust manifold and front pipe.
Given that this seems to work well I wondered if such was possible on a Dolomite.

To this end I acquired the gasket seal from a 2003 Picasso 1.6 petrol which proved to be too thick, however
(using a hacksaw) I cut it approximately in half, covered it in Hylomer exhaust paste (good stuff) and then
fitted it to the Dolomite (taking care to tighten gradually going from side to side).




Ian.

[Toledo Man]

As far as I'm aware, there's no gasket between the manifold & downpipe on the 1850. The end of the downpipe is flanged and this provides the seal. The clamp is just to keep the manifold and downpipe together. No gaskets or paste is required. When I removed the engine back in November on mine, the downpipe went back on without any problems.

[Jon Tilson]

The trick is to get both the manifold flange and the belled end of the downpipe clear of previous sealants.
The clamp usually needs a clean too. Wire brush or coarse w+d does the job.

Then its just a case of a smear of new sealing paste of your choice and a tighten up. You need decent studs, brass nuts
with a plain and spring washer on each and then when its all leak free you need to set up the gearbox clamp to hold it in
position. Without this you will be lucky if it seals for a couple of weeks.

Also I find the manifold to head flange prone to leaking as the manifold distorts slightly so you may need some gaskets
here if the metal to metal seal no longer works. Be careful as the bolts pull the threads really easilly on the head. Some
of mine are on helicoiled studs now which helps a bit.

Jonners

[cliftyhanger]

Many thanks all.
Will have a decent look at the weekend when I actually have some time to get under the car. The whole affair is a bit shonky really, but I guess the idea is to allow some flexibility. I like a decent pair of flanges, but then again I am old fashioned!
If cleaning up and fettling doesn't work, I will try the picasso gasket trick. You just never know....

Cheers
Clive

[MIG Wielder]

Yes, all good advice there. The only thing I would add is that the down-pipe to gearbox bracket may need slackening slightly to get it all to line up perfectly at the manifold and then tighten the manifold end at the same time as the gearbox bracket. It ideally needs a 2nd person to hold the down pipe firmly in place.
I also use the double length brass nuts. ( I think mine came from WINS International ). They cover the stud almost completely so are much less likely to rust in place. Use Copaslip on the studs but don't overdo the tightening as the studs can break.

[Toledo Man]

Jonners the manifold/cylinder head joint is a whole different story. They left the factory without gaskets but subsequent distortion of the mating face on the manifold makes a gasket necessary. It might be possible to get it absolutely level by sanding it down but it is just easier to use a gasket instead. Going back to the downpipe joint, it is essential to have it clean to ensure a gas tight seal. A few years back I bought a brand new exhaust manifold (Rimmer's had them on offer for £20 at the time) along with studs, spring washers and brass nuts. It might be worth replacing the studs, washers & nuts.

Tony, I had to adjust the bracket after I'd done my drive plate swap. I was able to use my crowbar to keep the downpipe in place but any similar implement will do the job. The brass nuts on mine came off without any trouble when I was taking the engine out. I'm not so sure about using copper grease on something that's subject to that much heat. I read something somewhere on a forum that using copper grease on cylinder head studs made them difficult to remove.

[Karlos]

If you are using brass nuts I think there is no need for copper grease. Brass is a copper alloy afterall. The point of using brass nuts is that they do not corrode onto the steel stud like a steel nut will with the constant heating and cooling. Also the brass nuts will have some deformation as they are tightened which may help in them locking in place, like a nylok nut but a bit more resistant to heat, so there should be no need for spring washers either. IMO