Exhaust downpipe bodge!

[Shawn]

G'day all,

I've had trouble with my manifold/downpipe joint for about two years, basically the whole exhaust has had it, but I'm not financial enough to buy a new one yet. The flange at the downpipe was so badly corroded that there was a chunk out of it, and the 'one bolt' clamp was not helping.

This is my most recent attempt at a fix (bodge!) It's really just a variation on the old "muffler blankets" you used to be able to buy:

1. Put car on stands to stop suspension movement when leaning over wing.
2. Removed carburettor for better access
3. Carefully cleaned downpipe and manifold joint faces of any old gunk, exhaust putty etc
4. Re-applied a small bead of exhaust putty to the joint faces (about half the recommended amount.)
5. With a sissor jack under the exhaust pipe, I carefully offered up the downpipe until it was firm against the manifold.
6. Apply small amount of putty around the outside of the joint.
7. (and here's the bodge!) Folded a sheet of aluminium foil down to about 40mm wide and 200mm long (about 16 layers thick) - wrapped this firmly around entire joint and moulded to fit as snugly as possible.
8. More putty over foil.
9. Another round of foil - not so much that the ridge of the joint is not clear - so you can see where to put the clamp.
10. Load a 'two bolt' type clamp with still more putty, and fit firmly.
11. Watch as 'worms' of putty squirm out everywhere!
12. Clean up with rag, run engine to cure putty

This looks a lot neater than it reads. I was careful to get everything as well aligned as possible

No more leak!!! (for the moment)

Any thoughts or better suggestions - It probably won't be long before I have to do it all again! (engine steady bar mounting is cactus - Mr Grumpy's conversion kit will be the next job!)

Cheers!
s

[rayofleamington]

The broken piece out of the exhaust flange is not uncommon when the joint has become unreliable. When it wobbles around it wears away the joint face on the manifold, so when you tighten it up next time it only makes contact on a few points - this leads to higher stressing as these small points pass on all the engine movement and vibration to the exhaust and hence those bits of the flange break away.

The cure is to change the exhaust manifold. A second hand manifold is very cheap but check that you're getting one that has no sign of wear on the joint face and hopefully all will become reliable.

[Willie]

Personally I have NEVER had to add any sort of 'paste'to the
manifold joint but seem to be in the minority. The best suggestion
I have ever seen is to insert a short piece of pipe internally into the
manifold AND the down pipe then clamp it up as normal. This seems,
to me, to take care of any missing areas on the flanges.

[Onne]

I did mine without any paste too Willie. works for the mo

[bigginger]

Same here for one of them - not the others though...

[rayofleamington]

I've done quite a few without paste and they all leaked. Having seen some new exhausts you wouldn't even want to bother trying it as the flange on one had the tube weld line sitting pround and others were not well formed. With a decent exhaust flange, I reckon it is down to the quality of the manifold flange area.

[ColinChandler]

Hello everyone,
I've done the piece of pipe up the inside dodge too and its fine. I think it supports the joint and stops any tendency for the exhaust to 'swing' about the cast manifold joint face and so break the seal.
Cheers, Colin.

[newagetraveller]

An old bicycle frame is the best source of tubing to go inside the exhaust pipe. Clean off any old paint and rust from the outside of the tube. Push it down as far as it will go into the (disconnected) exhaust then cut off the tubing so that about one inch sticks out of the top of the exhaust. Push tube up into manifold and connect the exhaust clamp.

Purists will probably have a fit about this as it does nothing for the flow of exhaust gases. It does stop it leaking though.

[Cam]

Purists will probably have a fit about this as it does nothing for the flow of exhaust gases.

Don't know about the purists, but the engine tuners will have a fit!! It will do absolutely nothing for the gasflow!! But then again, the Minor's standard exhaust system is hardly efficient!!

I don't think I'd ever use that method, but if it works........

[newagetraveller]

I have often wondered whether it is worse in terms of power loss to have a leak between manifold and exhaust pipe or a piece of pipe stuffed inside them.

[Cam]

I'd say the pipe stuffed inside would be worse due to the increased restriction (diameter, sharp edges, etc) in the standard exhaust system. A little leak might well improve performance!

[Kevin]

A little leak might well improve performance!

If you say so Cam is that a Welsh tuning mod then

[Cam]

Yes, it's a standard bolt-on performance mod. They have to be replaced every few weeks though as they fall off after rotting.....

[Kevin]

[rayofleamington]

A little leak might well improve performance!

I wouldn't bet on it - there's a few ppl out there that reckon a leak on A-series exhaust manifold will lower the performance. Personally I've never been able to tell one way or another.

[Cam]

Well, going on my personal experience of leaks, when I usually get a blowing exhaust, the performance increases VERY slightly, but more noticable is the performance decrease when the blowing is fixed. Mind you, I usualy let the exhaust blow for a while before getting a replacement exhaust/section. But I'm talking about high revs performance and not pootling about town...

[Peetee]

I have often wondered whether it is worse in terms of power loss to have a leak between manifold and exhaust pipe or a piece of pipe stuffed inside them

Use the right piece of Reynolds or Columbus bike tubing and you will reduce the bore by 0.8mm. That's right, it's 0.4mm thick!
But it would have to be 28.6mm outside diameter and I don't know if that's right for the inside of a Minor downpipe.