Air Pump noisey
 

The air pump on my 89 420 sel which works like an a/c compressor using a clutch to ingauge the pump.The clutch is only inguaged for about 2 min. and releases.During inguagement it makes a very loud noise,when not inguaged the noise stops.Apart from just pulling the plug and disconnecting the pump altogether, can this pump be rebuilt or is it on its way out?