My air pump is making a screeching noise at certain rpm's; 1200, 1600, 1900, etc. It's not belt slippage.

I took it to my mechanic today and he thinks the clutch in the pump is not totally disengaging and internal frictions may be causing the sound. He thought I would just have to wait until it got bad enough to have to replace.

I know these are very pricy, $800 new. Is there any way to repair the pump or should I start looking for a used one?

Not sure which car you are talking about but I was able to just change the air pump pulley/clutch on my E320.

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Jim

had same thing on my 88 560sel - air pump was a rusted solid mess inside - put in new air pump and changed the two valves that go to it. Works fine now - you are right - it is pricey. Some say disconnect pump it won't make any difference - I wanted my car to run the way it was designed.

Do a search on "smog pump" and "air pump" -- there are a number of threads. Rebuilt pumps are available for around $300 (you send the old one in for a credit) and are easy to install; you might as well renew the valves at the same time -- they're probably bad and played a part in the pump's failure.

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'98 C43 AMG
'88 420SEL
'93 190E Limited Edition (including factory Sportline package)