How do i fix my thermostat housing gasket from leaking.. Causing my datsun 1200 ute to overheat? I have replaced the gasket twice now.. and its still leaking? i have cleaned both surfaces for the gasket to sit.. Is ther maybe a slight bowe in the housing of the thermostat or something or ?what else could it be ?

Cars & Trucks - Datsun - 210 - 2005 Datsun 210