Lotus Elan

Sealing exhaust

PostPost by: 69S4 » Sat Apr 13, 2019 10:53 am

Over the last week or two I've dismantled the exhaust system and taken the manifolds off of my S4 trying to track down the cause of a leak. I can hear it on acceleration and I get some popping on slow-down. I've now cleaned everything up, checked the fit of the various bits, bought new clamps / manifold gaskets and now it's time to reassemble it.

My question is which sealants to use. I've a choice of high temp silicone or the traditional firegum style. Should I use the same stuff throughout - if so, which? or is one better than the other at certain joints?
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PostPost by: JonB » Sat Apr 13, 2019 11:59 am

Hi Stuart

I use a firegum type compound that is made for exhaust sealing, on all joints.

This stuff, to be precise: https://www.ebay.co.uk/itm/113146322223

I've had no problems.

Cheers
JonB
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PostPost by: 69S4 » Sat Apr 13, 2019 1:45 pm

That's what I'd normally reach for but everyone seems to be jumping ship to the land of silicone these days. And there's no doubt the stuff works - I sealed some bathroom fittings with a cheap version only yesterday. :lol: I was just wondering whether anyone has experience of how the posh version with copper or whatever's in it lasts in the exhaust environment.
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PostPost by: rgh0 » Sat Apr 13, 2019 2:05 pm

The high temperature silicone works well on the head exhaust gaskets which run cooler due to the head cooling , it burns off on the Y piece joins which are hotter I find and is then OK on the rear muffler joins which are cooler again.

cheers
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PostPost by: englishmaninwales » Sat Apr 13, 2019 5:12 pm

+1 for the HT silicone.
Plus it’s easy to remove with carb cleaner after dis-assembly.
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PostPost by: LaikaTheDog » Sat Apr 13, 2019 5:33 pm

I use gungum on loose old parts like tubular manifolds to Y pieces, and firegum on shiney new joints
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PostPost by: 69S4 » Sun Apr 14, 2019 6:06 am

I’m surprised about the manifold to head joint being cooler than the Y piece but I suppose it makes sense if you think about it. I’d have guessed to use the traditional stuff nearer the engine and change to silicone at the next set of joints. Just as well I posted here first :lol:

What’s the difference between gun gum and firegum? I’ve tended to use the terms interchangeably, thinking they were marketing terms for much the same stuff.

Anyone ever tried ‘moulding’ exhaust silicone? A couple of my old motorcycles use 2-3” silicone tubes to form a flexible seal between their manifolds and silencers and they’re all NLA at the dealers.
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PostPost by: LaikaTheDog » Sun Apr 14, 2019 1:37 pm

Gungum. Is used to patch holes, it bridges gaps... firegum is like toothpaste, the excess falls off.. gungum stays put.
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