I'm not exactly sure about your set up but if you using a metal gasket then I think the gasket sealer acutally makes it worse. If its the permatex stuff, give them a call, they are they helpful. 1-87PERMATEX (1-877-376-2839)
Permatex - Adhesive & Sealant Solutions...Made for the Professional is the website. The copper stuff Nagy was refering to is the stuff rated for high temp, the other stuff isn't supposed to work over 400 deg F. Hope this helps.