3.8 inlet manifold gaskets leaking

[Desmo]

Hello,

I replaced the 3 inlet manifold gaskets and used the items with article number C 14127/1 from SNGB. All metal contact surfaces were clean and not damaged. Before fiting the gaskets, I coated both sides with black silicone sealant that is approved for the engine/coolant area. After I adjusted the carburetors and warmed up the engine a few times, slight coolant leaks appeared on all three inlet manifold gaskets.

Was it a mistake to use silicone selant? Is it safer to use a non-drying sealant like Hylomar or are these seals to be installed dry? Are Cometic seals maybe the better choice and who offers them? Does a sealant have to be used with the Cometic items?

Thank you for your help
John

[christopher storey]

This is a very common problem irrespective of the type of gasket used and/or whether sealant is applied. It is usually the result of the manifolds "settling" as the engine warms up, and can usually be eliminated by retightening all the manifold to head nuts

[tim wood]

I had exactly this problem on a 4.2 with the combined manifold. I was using the tin gasket. After stripping off the assembly and cleaning up I went back to the fibre gaskets and all was well.

Tim

[Desmo]

Hallo Christopher,

Retightening the nuts unfortunately did not help.

Tim. What type of sealing material did you use when installing the fibre gasket?

John

[PeterCrespin]

hylomar is fuel proof, Room Temperature Vulcanizing silicone is not. Fuel might be puddling at the bottom of the ports and cause a leak when coolant gets up to pressure? Cometic are excellent but expensive, although they can be reused several times. Fibre gaskets are better than tin gaskets (which look reusable but are dodgy once the embossing is flattened).

Are you sure the leak isn't from the water rail gaskets or fitting?

If anyone wants a complete 3.8 carb/manifold kit I will advertise it again. Also fits a 4.2 with a bit of work...

[tim wood]

I think I used wynns instant black gasket maker. I’m aware however that should I ever want to remove the manifold then this will make it a right bugger.

[mgcjag]

Just fitted a fibre gasket and blue hylomar on a 4.2...works fine no leaks.....Steve

[tim wood]

Suggest you follow the advice from Steve .

[Desmo]

Thank you.

Tim I will try this way. We will see.

Best reagrds
John