is it ok to put the rotor housing into the solvent tank?
if not, how can i get rid of the black things at the side of the coolant sealling surface and make it seal good?

 

Solvent tanks are fine, but may not work well on some of the rtv sealants. Go ahead and soak it, then use a brass bristle brush on the mating sufaces. If the sealant is still sticking, try some brake cleaner. A wire wheel in a drill will speed things up.

 

excellent - exactly the answer i was looking for!
thanks!