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EXhaust Joints - to paste or not to paste that is the question?


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Just about to re-assemble some bit of exhaust after cleaning and painting (so not new) and just wondered whether it is better to use some exhaust jointing paste or just to fit dry. Someone invented it, so it must be a good idea - right? or is my ever present cynicism right to think it help exhaust companies/fitters boost sales making it more difficult to disassemble to replace just one section........


Any thoughts?

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This last winter I tackled a blowing on my manifold to down pipe junction on the Pig & a persisting problem on the Shorland.


The Shorland junction had to be regularly dismantled then jointing compound applied then after 20 miles it would start blowing again. I have since fitted a new down pipe in the realisation that the jointing compound will not seal a defect.


From several threads on a Land Rover forum I followed what seemed to be the most sensible advice. Don't bother with jointing compounds as they will not seal defects. Use generous amounts of copper grease. This will allow optimum mating of the flanges, the grease will burn off leaving a copper residue which may leave have some micro sealing benefit & the joint will be easy to dismantle.


I always find my tubes & tubs of jointing compound have always hardened up on me & copper grease is cheap & at hand. So I did the same to the Pig, but neither vehicle has travelled very far to test the validity of the seal.

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Apologies Robin, as you say a bit more detail always helps to make sure the advice is appropriate.


The exhaust in question is on my V8 Landrover Snatch. I had to take the middle two sections out to remove the gearbox and transfer box. Now I'm finally in a position to start re-assembly I was wondering whether to use any gloop on the joint.


Welded joints, 'fraid I can't weld been on my to do list for years so must sort that sometime. Also give that I if I've done something wrong I might have to take it all off again, I was hoping to keep it 'standard'. I've resisted taking the downpipes off as it all looks too rusted/seized so I would hope to avoid touching them if I had to take it to bits and at least the standard approach should mean I can avoid fiddling with these in the future if need be.




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Ring compression joints don't need any.


Flanges should be cleaned and dressed meticulously, a wipe of copper grease and a clean gasket should be sufficient.

Often, remaking a gasket in Klinger composite exhaust joint instead of copper-asbestos, results in a more compressible seal which seals better/lasts longer.


Slip-joints, it depends on the tolerances of the pipes, again a nice smooth fit should only require a good dose of copper grease.


I only use exhaust paste very lightly/sparingly, when there is a real need such as pitted flanges or loose-tolerance slip joints, but I always see it as a bodge to seal poorly fitted parts.


I openly admit to using it for 6 years to seal a RRC V8 exhaust manifold around #7 cylinder. It always blew very slightly, hardly noticeable under normal use but wouldn't pass the expert ear of the MOT tester. One fingerful of exhaust bodge would last 2 days before it fell out again, long enough to pass the test though.... :angel:


Alec :D

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