I had a strange moan from the 560 too, but it went away when I changed the accmulators. I suspect the moan had something to do with the "foamy" fluid when I bled the system down. With the rear of the car up on ramps, place a piece of clear tubing on the bleeder screw (to see the condition of the fluid and to allow for proper disposal) at the leveling valve, then loosen the screw just a tad (11mm I think). Caution, the rear of the car will settle as you bleed off suspension fluid. If the fluid comes out foamy, then the accumulators are probably shot.
You can't pull a fuse to disable the pump, it is bolted directly to the front of the block and is driven internally.
Try the bleed test and report back.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.