Noisy Smog Pump
 

Greetings all, after changing the rubber seal between the upper and lower front cover of my '91 300SE, a piece of cake repair BTW, I degreased the engine and after the rinse down (engine cold, BTW) the smog pump sounds like a bearing is running dry. The noise decreases at highway speed or acceleration and is most noticeable at idle. It wasn't doing this before the seal change, oil leak seems to be gone whew. What have I done by cleaning the engine?? I checked around the threads but could not find much. Thanks in advance

If the problem is the bearing in the pulley in the smog pump, instead of replacing the whole unit, which is very expensive, the dealer sells a rebuild kit, which is basically a replacement pulley with a new bearing. I think they run about $200, whereas a new pump is around $1,000.

Smog pump bearing source
 

check this thread: http://www.peachparts.com/shopforum/showthread.php?t=145362

Not certain but the smog pump referenced should be the same part as on your car.

I also have a slight whining noise in my engine bay which my mech thinks is the smog pump. The noise doesnt occur all the time though. I have changed all belts and still same noise sometimes. Noise goes away at acceleration or high speed.

The "non serviceable" pump is the same for all the M103 engines including the 2.6. That bearing is $19.00 plus tax and shipping.

Paul,
I believe you are thinking about the V8s. THe fiche shows a replaceable bearing for those pumps.

Actually, I was thinking about the M104 in my W124 E320. My independent Mercedes shop bought the pulley rebuild kit from the dealer when the bearing went out.

Geeez, you should have heard it. The bearing was squealing so loud, people would cover their ears when I went through a parking lot.