Air Pump making noise
 

My air pump on my 1996 SL600 is making a high pitch noise like something is rubbing and about to seize. The noise only occurs when the clutch is engaged during warm up.Is there any service that can be done on these before disaster strikes. I keep seeing these used on E-bay for about $1000.00.

I'm not sure how to fix it, but I know how NOT to: Don't try oiling the pump itself. The vanes may be made of graphite or similar and oil is supposed to degrade them.

I don't know about that particular pump, but some enterprising people on this board and the other got the bearings out of mid-80's models and a good bearing place should be able to match yours if you can disassemble it.

If it goes I know how to fix it. Purchase a bearing from and serpentine belt drive idler and make a pulley mount.

You might want to disconnect the wire to the clutch so that it doesn't engage. This might prevent failure until you decide what to do.

That a good idea. It's was quiet this morning.

I just replaced the air pump on my 95-S320 so I know a bit about these :). Bottom line is that the electric clutch will fail at some point and the entire pump seizes up once and for all. When that happens, the pulley will no longer rotate and the burning smell and blue smoke you see coming from under the hood is the serpentine belt rubbing on the frozen pulley.

My local import parts store ordered me a rebuilt pump unit for about $325 plus the core. There is a cheaper place on-line to get a replacement (http://www.mbpumps.com/, about $200 plus core return) but I know nothing about them so you will have to do your own homework.

Switching it out is fairly easy, remove the belt and remove two bolts (top and bottom, from radiator side). The top bolt is easy to find, the bottom one is under the pulley and you have to feel around for it. Loosen the hose clamps and wiggle off the two hoses connecting the pump to the exhuast system, and replace as needed. The MBPumps site says that you should also replace the check valve. To install the new pump, just reverse the process.

Getting the serpentine belt back in position was the hardest part! If you don't have a tool suitable to release the tensioner pulley, go to your local AutoZone parts store and they will give you a free loaner tool for a $25 security deposit. It makes the belt replacement a whole lot easier.

If I had to do it again, I could probably manage the whole job in 30-45 minutes.