When the accumulator diaphragms leaked the nitrogen into the fluid (on the 560) I noticed that the pump made a horrible growling noise. I thought it was the water pump at first, but couldn't pin point it. The hydraulic pump runs whenever the engine is running, so it does run all the time.
Soon as I replaced my accumulators the pump quit growling.
'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.