w124 Smog Air Pump rebuild
 

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.

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.

http://www.peachparts.com/shopforum/tech-help/172959-air-pump-bearing.html?highlight=air+pump+smog

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:

http://www.peachparts.com/shopforum/tech-help/145362-air-pump-bearing-solved.html?highlight=air+pump


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 I think it may have been replaced by the PO.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.

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.....

I agree. My pump should not make this noise. It is a rhythmic grating noise.

I picked up the bearings from two different shops. The big one is Chinese and only $19. A Japanese or German one would have been $35-$50. The smaller needle bearing was only $5.

JM,

Does the one you repacked have about 40-50 long thin bearings packed together?

Thanks,

glenmore

Road block on the way to rebuilding the smog pump! The bearing in the pulley on this particular smog pump is in there permanently. There is no way to replace this bearing as there are 6 crimps to the metal housing that hold this bearing in. This appears to be the variety of pulley that others have complained about costing $500+ only from Mercedes. I may try peeling off the seals and repacking the bearings, but I still have to get inside the pump and change/repack that bearing which is the one making all the noise. The pulley bearing feels notchy from lack of grease and you can hear the bearings rattle if you just shake the pulley.
The rebuilt for $200 is looking better and better.

glenmore
1991 300CE
2000 C280
1990 LS400

The bearing on my pulley is held in by several "pressed tabs" on the back side of the pulley. These tabs are the result of a punch being pressed into the metal pulley just next to the bearing. Replacing the bearing would require drilling these tabs. Once the new bearing was installed, new "press tabs" would be required to hold the new bearing in. I think it could be done with a few sharp blows on a drift pin. Fortunately, my bearings were still servicable.

I ended up making a "grease press" to grease the front pump bearings. (an idea that came to me while squeezing some toothpaste on to my toothbrush) I used a piece of radiator hose and some hose clamps. A picture is attached.

I reinstalled the pump. It is now very quiet when engaged.

J. M. van Swaay

Glenmore:

Sorry, forgot to answer your question. All my bearings were needle type bearings. Both the vane bearing needles and rear pump bearing needles were held in a race. I estimate the vane bearings had 8 to 10 needles, and the rear pump bearing had probably 18-20.

J.

I lost the nerve to rebuild my smog pump and went with a rebuilt for $225 from a local vendor. I had incorrectly concluded that the pulley bearing was not replaceable. This thread shows you how to do it.

http://www.peachparts.com/shopforum/tech-help/168879-air-pump-bearing-removal.html

The pulley in the oven, bearing in the freezer trick is one to remember. Not being able to cleanly press in the new bearing was one of my fears. Curious as to what brand bearing the shop used in the rebuilt, I popped off the clutch and sure enough it was the Chinese bearing that everyone is referring to. It is the larger one in the photo. The other bearing was supposed to be the inner bearing but the shop guy said it was too large.

Now most of the online sellers of rebuilt pumps require you to also change these 2 valves, the check valve closest to the engine and the diverter valve closet to the pump, in order for the warranty to be valid:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=22O14A4OD22Q03CZP0&year=1991&make=MB&model=300-CE-002&category=B&part=Air+Inject+Check+Valve

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=22O14A4OD22Q03CZP0&year=1991&make=MB&model=300-CE-002&category=B&part=Diverter+Valve

I don't know how they would enforce this but having changed my check valve ( as low as $15 if you shop around, otherwise ~$50), I can see the reasoning. The check valve is a simple one way rubber flapper valve with what appears to be a heat sensitive coiled spring shut off valve on the engine side. The engine side of mine was covered in soot. If the valve got jammed open than all this stuff would eventually make its way back to the pump. My diverter valve seemed relatively clean (plus it was $50+ for a new one) so I reinstalled it. The two rubber hoses were still in excellent shape after 150m, but I had new ones so I used those (~$20 for both).

glenmore
1991 300CE
2000 C280
1990 LS400

The air pump on my 420SEL is a Denso. During my continuing rebuild saga, see Chain Guides Replaced, I just checked the front pulley and it rotates just fine.

I also found that the A/C belt adjusting pulley was seized. I took the pulley off and oiled it. It's now silky smooth.

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.