I am assuming you have the two piece lip style seal. When you install the two piece seal rotate each piece a little so that the joining line does not match the joining line of the rear main cap. Check your pan rails with a straight edge and correct as necessary. Use RTV only at the corners where the rail gasket meets the rear main cap and the timing cover. DO NOT use RTV on the end gaskets. The one piece gasket is great, hope it solves your problem.