The air pump on my 92 300E has suddenly started whining rather loudly. How can I tell if the pump is failing or if it's just the bearing which I've read can be replaced?

The problem is almost always the bearing on the pulley.

A new air pump is about $1,000, but the dealer also sells a rebuild kit for about $250-ish with a new bearing.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

I read that the PULLEY BEARING 32BG05S18G-2DS in the proper number in another thread.

Did you replace just the bearing or use the rebuild kit?

I don't remember. I gave the receipt to the guy who bought my 1993 300E (3.2).

I had MB Stars do they repair (they post here on the forum under "MB Stars".

I watched them do the repair, but I don't remember if it just included the bearing, or the bearing and the pulley.

They removed the air pump from the car, removed the bearing and the pulley, replaced the bearing (and possibly the pulley), and reinstalled the smog pump in the car.

They were really fast. Took easily less than an hour, but they've done it many, many times.

Try sending them a PM, or call them. I've posted their phone number here before. Or you can call information for MB Stars in Walnut, California.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

I just did the air pump and compressor bearings on my 94 E320 2 days ago.

I got them both at:
http://bearingsdirect.com/products/index.php?action=category&id=56&subid=100

Easy fix for $30 or so per bearing.

John

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My 240D Gallery http://www.peachparts.com/shopforum/vbpicgallery.php?do=view&g=290

Pump out and pulley off. Bearing was very nearly siezed, could hardly turn the pulley by hand.

Question:
The shaft of the air pump turns freely but is rather noisy and does not turn super smooth. Is that a problem?

And how did you know which size bearings to buy? Was there some way of researching it beforehand, or could Bearings Direct tell you, or did you have to pull it out and inspect it?

You can take off the bearing and bring it to NAPA. They will measure it with a caliper and find a replacement SKF bearing (good quality) for replacement. I have also heard of folks just taking off the air pump since it is mainly just used for cold start emissions.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

In the E420 you cannot get away with taking it off because of the belt routing (need the pulley). Unless an idler pulley is fabricated for that spot.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified