Moaning & Groaning

[dpetryk]

I recently acquired a 560sel. It makes noise when the self leveling system is actively pumping oil into the system. As I ride around and the rear end dips down, you hear the oil being pumped. So as the car is bouncing around you hear little moaning sound usually for short bursts. Also when accelerating from a standing start (rear end dips down) you here this noise. The sound is only heard from inside the car. The pump is quiet and if you sit on the trunk and try to make the system pump up the rear end, you cannot hear and sound. It does pump it up however. I suspect that the noise is being transmitted directly to the body through the hydraulic lines or possibly the accumulators or cylinders. I am not sure if the pump is at fault or if this is normal. I suspect it is not normal to hear this noise. When I received the car there was a large leak in the high pressure hose on the SLS pump. I am sure it probably ran dry at some time in its recent history. Maybe the pump is damaged. It does not seem like the pump is bad but maybe it is hurt bad enough that its output has a lot of pressure spikes.

Does anybody know what type of pump this is ? Rotary vane or piston or something else?