Traditional Cork and Rubber Gaskets
Improper maintenance can ruin cork/synthetic rubber
composite gaskets traditionally used to seal such things as valve covers and oil sumps. If you overtighten the components these gaskets are sealing, you can actually distort the parts or crush the gaskets, which renders them useless. When
tightening stamped-steel valve covers and sumps, don't apply so much torque that the part being tightened begins to distort. This distortion, which is irreparable without completely
removing the cover you're tightening, will become the source
of a new oil leak and will certainly distort the gasket.