Thermostat housing is leaking

[COBALT]

I'm using the regular gaskets from NAPA, with some of that gray thermostat housing sealer that comes in a tube you get at the parts store. The gasket itself has a sticky side that goes to the housing. The sealer goes on the manifold.

I've taken it off, and resealed it twice. The stupid thing keeps leaking. Of course once it begins to leak the entire seal goes and then it leaks worse. The manifold and the housing are both clean, and I used 400 grit wet/dry sand paper to smooth them both off and take out the high spots so they're both flat. I'm also torquing both bolts to 25 ft-lbs. Since I had to rethread the short side I don't want to torque it any more.

I'm thinking about getting a new housing and a gasket from Mr. Gasket instead of NAPA. Anyone else have any suggestions? I'm getting tired of doing this same job over and over again.