Hey guys,

My girlfriend's car has a very slight leak where the cylinder head meets a smaller casting that holds the upper radiator hose.

The casting is pressed against the head and there is a sealant that goes in between the two. There is no gasket available, it's just sealant.

What kind of sealant would you guys recommend for this? I have some red high temp RTV and was planning to use that. Is that okay for sustained exposure to high temp coolant?

thanks!

Red RTV is for hacks, butchers, and illegals working on their Chevy in the parking lot at Walmart. Get a tube of Permatex "Ultra Black". It's used in place of a gasket on a ton of OE applications, including oil pans on a lot of cars built since the mid 80s.

When I see the red stuff, my estimate goes WAAAAY up, because I know I'll have to fix what the owner, or the previous wrench, has already "fixed".

The Cap'n

I agree the grey stuff is good. Pull the outlet off and make sure you clean it thoroghly. Then place a piece of sandpaper on some glass and make sure the outlet housing is flat. Then put a very small amount of sealer all the way around the housing.

I use Honda bond but if you are only working on this one project it is pretty expensive, but it is great for all things sealing.

Thanks guys! I have that unopened tube of RTV for some RC car application that i forget at this time. It looks like it's some grey stuff that's already on there, so it's probably honda bond or permatex as you guys say.

Thanks again, she'll be happy!

Yamabond. It's formulated for aluminum. It's semi-hardening. I've repaired active oil leaks with the stuff. I had one of the kids use it on a cracked aluminum oil pan. Dries slower than JB weld but will not soak up oil and come loose.