If it has a cork gasket on it you could have over tightened it...I use the gorilla snot like bjuice said and a dab on the corners where the rubber end seals overlap the side gaskets..after the pan it on I take black or grey silicon an use my finger to fill in the little void between the pan and edge of the gasket..all the way around ... sorta squeegy(sp) it out with my index finger and then wipe off excess and it just looks smooth around the edge and never leaks