RTV use

[DeanR]

Can RTV be used to seal some gaps/seams in plastic (waterproofing)

[JACKHAMMER01]

For plastic I would use silicone instead of RTV. As far as using it on the engine, just remember that RTV actually means "Really Trashes Valves"

RTV will actually shrink away from the plastic, as it contracts and expands. Silicone won't.

[DeanR]

Hmmm, what I have in my hand says Napa Black RTV Silicone Rubber Auto Sealant..

[JACKHAMMER01]

Once again, RTV will shrink from weather changes. Now, with that said, the Black RTV Silicone Rubber Auto Sealant that you have in your hand, is different from regular RTV. That one has a higher concentration of silicone in the mixture. Check the packaging, to make sure that it is Non-hardening. If it is, go for it. But if it dries hard, I wouldn't use it. But the choice is ultimately yours to decide.

[t3rmin]

RTV is a type of silicone is a type of rubber...

I'm fond of "Shoe Goo" as a high strength adhesive sealant.

What are you trying to do exactly?

[DeanR]

I'm just needing to fill in some gaps in some seams in the bodywork on my Honda as I put it back together. There are some spots that I don't want water finding it's way into. Figured black silicone RTV sealant would work well with black plastic. I hate all this plastic on the ST.
XS = much better in this respect

[JACKHAMMER01]

Another option is to use a Plasti-Welder. Works just like the wood burners I played with as a child, only with plastic. Can be bought at Lowe's, Home Depot, places like that.

[prometheus578]

Works just like the wood burners I played with as a child,

Are you gonna burn your fingers... or chase your brother around the house like I used to?

[JACKHAMMER01]

Actually, I used to sneak up on my little brother, hold it close to his ear, and then dare him to move! My Mom would beat the s*** out me later, but watching him sweat was worth it!