Having some issues with a small exhaust leak from the exhaust manifold on my campervan. We got it taken to a mechanic to repair the manifold leak but he's ended up just making it worse. I dont have the tools to smooth out the Manifold myself, so was wondering if there was any putty that could withstand the temperatures of the manifold I could use?

Ive already had a crack at using fire putty - it worked perfectly for the first 20 mins but then failed, presumably it couldn't withstand the temperatures. But if someone knew of a type of putty that would work on exhaust manifold temperatures that would be fantastic.

  • The first Google hit is for Pyro-Putty which seems to be designed specifically for exhaust systems. Commented Oct 28, 2023 at 17:20
  • Back in the day, the standard stuff for this was Gun Gum. I don't know if they still make it.
    – Chenmunka
    Commented Oct 30, 2023 at 11:41
  • Asbestos makes best muffler sealant but is politically incorrect today. I made pretty good stuff with asbestos and sodium silicate. Commented Oct 30, 2023 at 15:40
  • @blacksmith37 for a moment I thought you were joking, because in UK it's been illegal to use asbestos in any product since 1999, but I see that's not the case in USA. Mesothelioma.com says "many products still legally contain up to 1% of the mineral". Not that in itself could be dangerous here (it's the dust which problemmatic), but there are workers in factories that import and process it. Commented Oct 30, 2023 at 20:21
  • @Bren how old is the exhaust? One mechanic made it worse which suggests that it may be time to replace all or part of the exhaust system. Commented Oct 30, 2023 at 20:28

1 Answer 1


Leaking exhaust manifolds are serious, as the exhaust fumes could leak into the passenger compartement.

A bandaid in form of putty won't stop the leak.

With a bit of luck you only need a new gasket. Otherwise the manifold is cracked and needs to be welded (since it is cast iron you will need a professional welder) or replaced (ask at a scrapyard).

The bolts holding the manifold are notorious for being rusted. A oxy flame could be helpful. Cover the new nuts with anti-seize before assembly.

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