Progress! After another trip to the dealer to get the 2415 ($67 ouch) which I will need to run the air pump I confirmed the belt is too long without it. The 2257 is too short so WTF? After looking at my RENNTech 3.6 and Euro motor w/o air pumps I finally realized the alternators are mounted where the '91 air pump is mounted! This explains the missing length of the 2257 belt. The air pump bracket is different from the alternator bracket but maybe it can be moved up. It's too late to work on the car tonight to find out. At least I know I have my Euro motor's alternator bracket that I can use. I feel better now that I know I can get everything to fit. The only question now is if there was any more damage caused by the locked bearing.

Unfortunately registration renewal just came in the mail so I'll need to smog this car. I could chance it and see if they'll pass it. I still plan to find a good used or rebuilt smog pump or just get a replacement bearing. I found a source here: http://www.auto-pac.net/pages/store/...et/displayroom

Still don't know why the dealer sells the 2257 for $20 and the 2415 for $67...

Thought I'd show the carnage to warn you of the danger of a squeeling air pump bearing...

Hmm.. - Things apparently were getting hot under your hood..

Anyway, in gpracers picture, my belt layout would be the upper one withouth the aircompressor. Although my engine is the 104. The belt length there would be 6pk 2330 - 6pk 2355. Both lengts should work, since my newly installed belt is 6pk - 2355. But I also replaced the wheel number 9 with a new one, and that was just a little bit larger.
-Had no trouble rerouting the belt, however. Just removed the fan clutch and by then it was all fairly self explanatory..

Oh, and if you´re gonna adjust the belt tension yourself, don´t forget to slightly loosen the tensioner locknut first ! It´s a 19 mm hex nut located slightly right and below the tensioner wheel itself. You´ll find it if you look closely.. Then you can adjust the belt tension with a 13 mm socket and an extension from above.

cheers,

Is the belt routing the same with the 104 as the 103?


thanks
Brian

Yes it is... same as the images gpracer posted. The only variant I could find is that some models that have no a/c compressor have an idler pulley at the location (No. 3).

A 2330 or 2355 may work for my current configuration w/o the air pump but the parts guy at the dealer said I can only give you two options as shown in the computer (unless I had the full part number). Maybe the parts guy at the other dealer will have more creativity...

How did you get a larger idler wheel, got a part number?

I thought all North American cars came equipped with A/C. Seems odd a Mercedes would not have it.

Good advice on the tensioner locknut. I've found two of my previous cars had bent adjuster screws.

Anyone know how often to replace the engine dampener attached to the tensioner?

I bought a air pump last night online, only $205 + core shipped: http://mbpumps.com/?src=overture

Well, I simply ordered a new idler wheel and got a larger one by mistake
And since I couldn´t be bothered to bring it back, I just installed it. I loosened the tensioner locknut and pulled the belt until the tensioner gave some more slack, just enough for installation of the belt. Then I retensioned the belt and tightened the locknut... etc. -But note, that I still have my airpump installed and therefore the unchanged belt routing. I picked up a used pump from a parts dealer..
I´ll see if I can rebuild the old one when I find the time.
-The new belt is the same length as the old one, so both size idler wheels work on the same belt length and therefore It can be assumed that certain clearance in belt length is possible on every belt routing. You just have to adjust the tensioner accordingly.

-My car is not North American, and does not have A/C. I am in Europe, Iceland to be excact and imported my car from Germany some three years ago. Don´t know if all North American cars ar equipped with A/C or not..

But sorry, don´t have the part number of the idler wheel. I´ll see if the number is visible without removing it, though.

Cheers,

Well, it apears as if I'm entering this thread a bit late.

I had my air pump / smog pump seize up on me around a year and a half ago. The noise it made was so loud I can still remember it like it was yesterday. The pulley just seize up due to the bearing failing, jamming the pulley into the pump at an angle.

I ended up getting a rebuilt unit rather cheap, around $200 from this machine shop in North Hollywood. If you need the location let me know.

zeronero,

Thanks but my last entry shows I purchased an air pump at mbpumps.com for $205. Installed it and was good to go. No further damage other than stated. I wanted to run without it but the smog requirement in the registration renewal came in the mail. I also found out I would need to either find the correct shorter belt (not the 2257) or install the alternator brackets from my Euro motor which locates it higher up on the engine to be able to use the 2257 belt. One bracket came off easy but the other bracket was behind the crank. I'm fine with it, it's smog legal and other posts indicate it doesn't do much harm (robbing hp, or it's additional weight).

True, since it's on only for the first minute or so of cold start up.

Well, glad to hear it's all finished, next time I'll read through the posts more thoroughly

I wonder if you can put an air conditioning clutch on the thing so you can disconnect the air pump five minutes or so after a start. That way you can dump that constant, horsepower sucking load.

As preventive maintenance, how about disconnecting the discharge of the pump and while the pump is running, shoot a bunch of molykote into the suction to lubricate/coat the air pump's internals.

My old mustang had a pump that failed, I just removed it. My tinkering spirt, I dissected the pump and found that the root cause of the failure was water getting ingested into the pump. The inside face of the bearing was unprotected and the water tore it up.

The pump only only runs until the engines reaches it's normal operating temp., which only takes around 2 minutes after cold start. After that the clutch disengages and the pulley spins freely so there really is no loss of power.

It seems that most people have problems not with the actual pump itself but with the pulley since the bearings eventually go bad. Since the pulley is part of the pump it's sealed on and can't be serviced normally due the the fact its apart of the emissions system.

hello, I got a 91 300ce , trying tu bypas the air pump, the dealership says there are two belts for my car 2415 and 2440 mm, I am trying to figuife out what size fits and where to find it. All the places I call say we dont know how long, just te`ll us what kind of car. Where an d how do I figure out what size belt and what do I tell the partys guy at these stores what it is , Are they being dumb, or it copuld be me!!!!! Thanks

If you read the thread, mhorn posted # 6 PK 2257 008 997 7092 for AP delete.

The number is the loop size in mm. You can fit a wire around the pulleys (except AP), allow room for tensioner adjustment to give you the correct length. You may have to convert it to metric.

I live in South Texas and have no emission laws yet. My air pump pulley seized.
I have a 104 motor with 24 valve engine (104.980). I see some discussion that folks removed the air pump and bypassed it. The belt folks have used is 6PK2257
is this the right belt without air pump for this engine?
The question is what to do with the rubber hose which has two check valves.
Does one leave it alone disconnected?
please help as I think I don't want to spend $300 for a rebuilt air pump when it is
not required.
Thanks a bunch

As a data point for others deleting their smog pump from a 3L engine. Using the belt from pre-89 engines that did not have the pump will be way to short. Pump is mounted in a different location.

Auto Zone part number 935K6 or new number 6PK2375 fits great. Maybe able to get the 930K6 on but it would be a real bear to get over the last pully. The 940K6 will not be able to be tightend enough to get proper tension.

93.5 inches or 2375mm.

great info on the belt size to bypass the smog pump.
I just put a new bearing in the pulley but i think my smog
pump is bad as it always stays on even though I unplugged
the electrical on it, possibly the clutch is bad.
So, I am just using the pump pulley which now turns freely with
the new bearing.

I have a 1990 300E 3.0, German engine, I want to eliminate the air pump,
what size belt would I need ? part number ? what stores have it ?
can I adjust the alternator without buying another belt ?
Thanks.

94 E320 can you help me with a belt size w/o smog pump please