Good news!

The smog pump is designed only to operate for the first 2 minutes of cold startup, not while running, not on hot start. So the power loss is really negligible. Yes, it's an extra pulley to spin. But if it's functioning as designed you should never know its there. Which is why I decided to replace mine and it's good for the foreseeable future. And the car stays as designed, no weird belt, etc.

__________________
http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...

I would have been happy with "an extra pulley to spin", but mine wasn't spinning! lol.

That's also why I wouldn't have any problem gutting it if the internal bearings failed, but the pulley was fine...

__________________
Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress

My '91 SE has a clutch on the smog pump, just like the AC compressor.
It engages for a couple minutes on cold start, then disengages and just turns the outer idler pulley, not the pump innards.
If you don't want the pump to run, just unplug the wire?? and it freewheels on the idler bearing. If the idler bearing is bad it can be replaced with a std bearing part number as I remember. My pump got a bit noisy about 5 years ago, had the wire unplugged ever since. Has no effect of smog test, as they test it with the engine warm, when the clutch would be disengaged anyway.

Maybe the E-class is different??

DG

Ooops. Never mind; I reread the post - your idler pulley bearing was indeed bad.
I'll go back to sleep.

Dg

Does anyone know where all the hoses on 1991 300e 3.0Lt. Meaning the smog pump hoses, I have the bottom one conected just dont remember where the top one go?