Suggest you search this site using "A.I.R. Pump" as the key word.

On my 560SEL the noise became an issue. From the archives it was evident that the clutch/pulley was the issue, not the pump itself. Bits and pieces dropped out of the clutch assembly. I removed the belt, noat the pump. The noise stopped. I now have to decide whether I want to spend the ~$300 for a rebuilt pump from Fast Lane.