I have had an E type jaguar coupe and roadster since 1963, an xk 120 and a 3.4 sedan and must tell you that they all leaked oil at the rear of the crank shaft. The only cure that I know of is to take the engine to Bill Terry in Benton Illinois and have him rebuild the engine and install his modern rear main seal. He turns the thread off the crank and has a modified seal housing that accomodatby 38eots - Jaguar E-Type Forum