Noise coming from fan area on 89 300E
 

I have an 89 300E with about 110K miles. It developed a noise that sounds to me like a bad bearing somewhere in the front of the engine. My guess is either the water pump bearing or fan bearing or some other bearing. Can someone tell what is a common failure and or is there someway to diagnose what's bad before I take it all apart. the plastic fan spins freely when the engine is off.
Thanks
Jerry

The belt idler pulley went out on my '87 300E at 120K in one of the most remote parts of Washington State.
Anziani
'93 300CE 174K
'95 E420 117K

Does your model have a smog pump? If so, those can get pretty noisy when they start to go bad.

you have to go in and check.. All of the pulleys are susceptible to failure.. Try loosening your belt ( loosen big tensioner bolt 1/2 turn, unscrew tension rod) then wiggle your pulleys one at a time. They should have no slop. Usual culprits are tensioner pulley, idler pulley, a/c, or maybe the fan pulley housing. Its different every time.

Mechanical Stethoscope...........

And don't forget the bearing in the alternator.
Mine whistles on low rev's. Am about to get a replacement today.

Likely the fan bearing bracket... although the air pump idler bearing also seems to have a low expected useful life. Check the fan from the side, the blad should not wobble fore/aft, if it does then you MUST get the bearing bracket looked after SOFORT! Failure of this bearing will almost guarantee the additional cost of a new radiator, belt, and fan (and likely a tow too).

Another rule of thumb... if one of the other idlers goes wobbly, the others will not be too far behind. Once you have the belt off you are best to replace them all... including the AC clutch bearing which you wil need specialized tools to get at (Autozone might have them for loan).

Thanks to everyone for the inputs.
I had already tried a stethoscope made out of a piece of garden hose, but it didn't work very well. I'll have to get a better one. I assume I have to take the radiator shroud and radiator out to get at these pulley's.

That is why I mentioned a mechanics steth.
They have a long metal shaft that you can slip right into each part as it is rotating..they are $5 at most discount places.
Garden hose is not applicabe for vibrations........

I replaced my fan bearing bracket + smog pump idler @ 120k miles and now at 145 k miles the A/C bearing is in need of replacement.

I would say if you hear strange things in there just go ahead and replace them all (fan bearing bracket, smog pump idler, A/C bearing, 2 idlers). They usually fail within a very short interval of each other anyways and the parts really aren't that much (with the exception of the fan bearing bracket).

Dedicated idlers you can get @ the Benz dealership, the smog pump and A/C pulleys you can get the bearings pretty inexpensively at www.bearingsdirect.com provided you have the dimensions (which you can easily find on eBay if you know your smog pump and compressor model).