I gather from the threads that the typical problem with these pumps is the bearing in the pulley. That repair is straightforward. There is a fellow on ebay that sells the bearing along with instructions for $50. I am pretty sure that my problem is the inner bearing, i.e. the pump makes noise on startup only and when it clicks off, the continuous running pulley is fine. Anyone replace the inner bearing? Difficult? The fellow on ebay suggests just to relubricate this bearing.

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

I'm working on this same thing myself. Any chance you could post a link to the Ebay item?

I've disassembled the pump (see picture) but I can't figure out how to get the front pump bearing out. I may just clean and lube, put it back in and see if it's quiet.

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You can just unplug it, until your next smog inspection comes up.

I bought a replacement at Cvj Axles out of Denver.

Steve

Here is what I've found so far.

Here is a thread that has some good descriptions, plus the pulley replacement bearing and the online place to buy them.

Air pump bearing

This place is local to me, and I was hoping to drop by and pick up the bearings, but they did not answer the phone. Website appears to be up, hopefully they are still in biz.

Here is the ebay guy:

http://cgi.ebay.com/ebaymotors/Mercedes-Air-Smog-Pump-Repair-190E-300E-E320-260-etc_W0QQcmdZViewItemQQcategoryZ33610QQihZ013QQitemZ230118965305QQrdZ1QQsspagenameZWDVW

There is some good info just in his ad. He does not have any current auctions. I emailed him with a few questions and he did not answer, you may have better luck.


Here is a current auction for a rebuilt unit:

http://cgi.ebay.com/ebaymotors/87-96-Mercedes-Smog-Air-Pump-Part-33-320_W0QQcmdZViewItemQQcategoryZ33610QQihZ003QQitemZ130104968389QQrdZ1QQsspagenameZWDVW


He is local to me and if I get into a jam, I may buy this one.

Here is another thread I found with lots of detail:

Air Pump Bearing - SOLVED


I suspect that my vane carrier rear cover bearing is shot so I'll need one of these Timkin bearings also.

glenmore
1991 300CE
2000 C280
1990 LS400

Thanks for the links.

My pump makes noise only when the clutch is engaged, the pulley bearing is OK. I think it may have been replaced by the PO. The internal pump bearings appear to be in good shape. I have successfully lubricated the front bearing, it is now quiet and smooth when I spin it manually. My theory is that when the rubber vane material wears, it leaves behind a dust residue. This dust gets in the bearings and causes them to make noise. I'm hoping that a good cleaning and a bit of grease will work.

I'll let you know what happens when I reinstall it this weekend.

That means it's working properly. All of the smog pumps do the same.

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http://search.ebay.com/_W0QQsassZkhazenzcc

I have two 124's with the same engine (104.992) and smog pump. One runs very quietly when engaged, the other makes lots of noise. The one that makes lots of noise is on a 200,000 mile engine, the quiet one has 93,000 miles.....

Anyone remember or have an exploded view how the vanes go back in? Thank you.

Bump

Anyone remember how the Vanes go back in. In my rage I forgot.