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?

Well, it is a pump. I'm not sure, but the noise may be the pumping action.

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95 E320 Cabriolet, 159K

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?

I actually got the part numbers of some threads here. I don't have my order handy, but I will post the numbers later today. If it were me, I would replace the bearing and see how it works. If the pump later gives serious problems, just disconnect the power to it, and the pulley will simply idle on the new bearing. From what I understand the air pump only works when the engine is cold, so you might even pass an emissions test with a warm car (really the only way to test a car anyway). If you do disconnect it, I assume you may have to clear the check engine light occasionally.

John

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

My vehicle is 92 300E. Bearing measured ID:32 mm x OD:52 mm x W: od 18 mm + id 20 mm

That is bearing 32BG05S18G-2DS the person at bearings direct told me they are made in China, hopefully they will be decent quality. I ordered 2 bearings since I have another 1992 300 TE.

In the meantime I took the bearing seals off of the one I removed, cleaned the bearings, blew them out with air and then regreased using Mobil One synthetic wheel bearing grease and reinstalled the seals. It felt like new as far is being smooth and tight; although I have no idea how long it will stay that way.

I put the bearing back in the pulley and the air pump is now reinstalled on the car and it is very quiet.

Hey guys,

I've been going through a '90 300SEL over the last few weeks. On the list of things to take care of is the noisy bearing in the air pump. Now I know there've been posts to various lists about where to buy a new bearing and all that, but I figured some of you may not know you can just clean up the original bearing and repack it with grease.

This doesn't always solve the problem with a noisy bearing. But some of the time, especially with something that's ten or fifteen or twenty years old, the problem is largely that the grease has just dried up. If you catch it early enough, you can sometimes quiet it down again just by cleaning it out and repacking it. Sometimes you go through all that and the bearing is still noisy, but I gave the first method a try, and in this case it worked out fine.

I just popped the belt off the pulleys, pulled the hose off the back of the pump, removed the two mounting bolts, and pulled the pump up to the right a bit behind the headlight so I could get at the front of it. Before I loosened it, I used a Sharpie to mark the clutch mechanism's retaining nut in relation to the shaft so I could tighten it back to the same spot.

I tried holding the shaft still with a hex socket and ratchet while using a box end wrench to loosen the nut, but that didn't seem to be working out so well. So I bailed on that idea and just used an air impact wrench to knock the nut off. It's a normal right hand thread, not a left hand thread, so... lefty loosie righty tighty just like usual. With the impact wrench it was jut a quick zap and the nut was off. The clutch pops right off. Then I removed the snap ring holding the bearing in place. When I tried pulling on the bearing, it seemed locked onto the shaft pretty solidly, so I hit it with a bit of PB Blaster, went for my 2 leg puller, and the bearing and pulley came right off pretty easily. I think it would have been fairly tricky without a puller though.

So, here's the part some of you may not be familiar with, removing the seal to clean and repack the bearing. You basically use a minature screwdriver to gently work your way in under the inner lip of the seal, then pry the seal up. Be cautious not to tear the lip of the seal. If you bend the inner metal plate a bit, it's not the end of the world. Just straighten it out with your fingers after you get it off the bearing. The bearing was totally dry. I hit it with some brake cleaner, spun the bearing around a bit, blew it dry with compressed air, repeated that a few times until it looked clean, then used very high grade Mercedes air pump bearing grease to repack the bearing.

Okay, that's a lie. I used some WalMart Supertech EP multi-duty high-temp that I had sitting around. I just worked it into the bearing with my fingers, then popped the seal back on and put everything back together. It seemed to have taken care of the noisy bearing.

The seal's a bit tough to read in the pics. The text on it reads:

INA W.-Germany L32/52 2RS AH03 *Mercedes star* 001 981 42 27





Patrick

Here's the air pump info from the "buy parts" link at the top of the forum page:
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Vehicle 1992 Mercedes Benz 300E
Part: Air Pump

Note: Remanufactured
with pulley.
Engine: 12-181462-


Product Brand Availability Retail Our Price

B6010-50260 Air Pump Remanufactured IN STOCK $663.95 $485.86


B6010-71761 Air Pump IN STOCK $1350.00 $1097.37

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1986 560 SEL (159K miles)

Thanks guys, this was a terrific thread, sure beats buying a used or rebuilt pump.

I tried to clean up the bearings but the plastic bearing separators were melted, globbed up, and jamming the bearings. Hence the bearings once cleaned were toast. I regreased the bearing but there is now so much space between the ball bearings that it is still quite noisy, not to mention the seals ooze grease... too much put in perhaps. At least it's not seized now, and my bearing is on its way to me from Bearings direct.

The size is different for my '95 E420... OD: 46mm, ID: 30mm, Width, outer race: 18mm, width inner race: 16mm, with inner race face aligned with outer race, not centered.

Bearing direct cost, with shipping & tax, $30 and change in Nov 2009.

Tchew,

Do you have a part number for the E420 bearing?

Thanks.

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

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