To RTV or not to RTV?

[maillemaker]

I'm about to replace the thermostat housing on my 1995 Mustang GT with a version that is NPT tapped so I can install a temperature sensor.

I've seen some YouTube videos where they replace a thing with a gasket that you should "let the gasket do it's job" and no RTV is needed.

I did this job on my 1990 E350-based RV and the first time I just used the gasket. It leaked. I then went back with gasket+RTV, and no more leak.

I like to put a thin layer of RTV on either side of the gasket. It just seems to work.

What do you think?

 

[ctandc]

Depends on the engine / application. Aftermarket water housing? I'm likely to coat the housing, lay the gasket then coat the other side.