Gasket questions

[AustinJ]

I've got a couple of possibly silly gasket questions, but I figured better to ask you guys and be sure, than assume something and have leaks.

I am replacing my water outlet neck and thermostat cover with the beautiful shiny pieces I just had coated (Thanks Jdub!!). When I pulled the various sensors out to put them in the new coated pieces, I noticed there was some rubbery goopy stuff at the top of the threads. Should I use a sealant when putting these sensors back in? What kind, just some high-temp silicone or something like that?
Also, where the water neck attaches to the block, there's a gasket, but there was also rubbery looking stuff there as well. Is the new gasket enough, or should I use some kind of extra coating for it to help it seal, and what kind should I use?

Thanks!

 

[Nomad707]

the rubbery goopy stuff is silicone.
some use it, others dont. i use a gasket sealer, the brown glue of gods.

 

[IJ.]

On tapered thread fittings I use Plumbers Teflon tape, the "goo" is just a liquid version of that.

 

[Poodles]

the new ones from toyota have some kind of clear sealant on them. I didn't use any sealant on my old ones and I'm leak free...