I'm using silicon for the fittings on my reservior. I have brass fittings sealed using a silicon goop. My question is, how strong is the hold on silicon. Will it come off easily. Does it cure to plastic well?
The silicone based thread sealer I use on my car is the best. I use it on the fuel system rather than teflon tape, the tape can lose small pieces, and plug jets in the carb. But I don't think that would be a problem with your water cooling setup.