coolant leak

I used to own a rad shop and we always sandblasted our housing and repainted them. a good way to check for trueness is to place the housing on glass, a door window or something, and see if it is flat or if it rocks back and forth. I also swear by Mr. Gaskets "The RightStuff" its a black gasket sealer that would seal the hole in the dam somewhere in Holland it works that good!