My 89 560 SEL has developed a very unusual problem. When doing highway driving I lose engine oil and the suspension leveling hydraulic pump starts overflowing creating an oil slick down the entire drivers side of the vehicle. A check of the fluid in the suspension pump indicates that it is engine oil in the pump. Originally, it was the proper hydraulic fluid. Questions: is it possible for engine oil (given a worn seal) to flow from the engine into the pump? How do I determine if the problem is the pump itself or the seal between the pump and the engine driven shaft?