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Posted by: black73 May 16 2007, 03:15 PM

I have a '92 Pontiac Grand Prix with a huge oil leak where the intake manifold meets the block. There is no gasket in the area that leaks, just black RTV sealant. Since the RTV has failed once I have no doubt it will fail again, so does anyone know of a better way? Thanks

Posted by: bondo May 16 2007, 03:42 PM

They used to use cork gaskets on 'merican V engines, but with newer emissions requirements, the crankase is no longer vented. Cork gaskets either get blown out or sucked in, so RTV is the replacement.

The trick is to use a good quality RTV (I like "ultra copper") and make sure the manifold and block are VERY clean. You will need to remove the manifold, and replace the manifold to head gaskets. Put the new gaskets on the very clean heads, and run a nice thick bead of RTV on the block sealing surface, overlapping onto the gaskets on the heads about 1/4". Then set the very clean intake manifold in place, but only tighten the bolts finger tight. Make sure the bead made contact with the intake, if not you'll have to add more.

Here is the key: Let the RTV cure for at least several hours before torquing down the intake. This not only makes sure the RTV is bonded to both surfaces, but it also puts the RTV under pressure so it can't leak.

Posted by: Jake Raby May 16 2007, 03:45 PM

Loctite 518. Job done.

Posted by: bondo May 16 2007, 03:58 PM

Hmm, mcmaster.com says:

Adhesive gel forms tough, resilient seals to replace gaskets. For difficult-to-seal aluminum flanges. Fills spaces up to 0.01". Temperature range is -65° to +300° F. NSF/ANSI-61 certified for use with drinking water systems.

In my experience, the manifold to block gap is more than 0.01", but I've never actually worked on a 92 grand prix, so I can't be sure.