Can RTV silicone (e.g. Permatex) be used for valve cover gasket material?

Or will it cause problems?

 

Depends on the application. Some vehicles have perfectly flat surfaces that don't take a gasket, but instead take RTV as their sealant and it lasts a very very long time when applied correctly. Typically, you will see that sort of setup on aluminum block or aluminum head engines, as the porosity and manufacturing tolerances allows for better sealing with RTV rather than a gasket.

If you are referring to 1st gens taking RTV instead of a gasket, don't do it. The surfaces were designed to use a gasket ALONG WITH some dabs of RTV in strategic locations to help improve sealing in areas of questionable sealing reliability.

 

If it uses a rubber type seal, probably won’t work. The RTV is designed for tight tolerance joints and seals.

 

When I bought my truck last month, the previous owner had a professional mechanic replace the valve cover seals. He used RTV. Guess what? It's leaking.

I spent good coin buying all new parts...half moons, cam plugs, valve cover seal, valve cover washers, spark plug seals, intake runner gasket, throttle body gasket, and Toyota FIPG sealant. Going to do it right. I never understood why some people go through the trouble of doing it wrong especially when the process takes a few hours at the minimum if not days for a noobie.

 

My experience has been when people have used sealant, it’s been done incorrectly or with the wrong product. Or just not allowed to cure properly before use.

You can use it in a pinch but if your application requires gaskets, use the gaskets.

 

If you’re just asking about putting it on the half moons and the small areas the FSM says to put it, then you are good to go to use any RTV, but if you’re asking in place of the factory rubber gasket then it’s a no.

Just make sure you let it cure a little before running the engine and also read the directions about how much air time you have with it. With Toyota RTV it only gives about 5min or less before it starts to cure and get a skin which isn’t good for creating a tight seal