Hello all,

Vehicle: 1992 300E 3.0L AT 122k

Problem: Last night while tooling around town a loud, rpm dependent whirring noise developed. It is present in all gears including park and neutral. This morning when I started the car the noise was still present. I got my trusty stethoscope and began listening. Unfortunately, when I placed the stethoscope on the transmission dipstick tube the noise was very loud and there was a lot of high frequency vibration in the tube. The fluid is to the proper level and clean. The filter has been replaced within the last 10k.

Threw caution to the wind this morning and decided to drive the car to work. Low rpm in gear cause the noise to get louder. Other than the noise the car drove beautifully and shifted perfectly.

Questions: Has anyone had the transmission pump fail with only 122k? Did it make a whirring noise? Are there other parts of the transmission that can make this sort of noise?

Thanks in advance for your help.

__________________
Kyle Fitzpatrick
Materials Engineer

1969 300SEL 6.3
1992 300E
1994 E320 Touring

could be fan clutch!

Maybe the starter bendix gear isn't fully retracted?

Maybe something got through the bell housing mesh and is hitting the torque converter?

Sixto

I would startwith belt-driven accessories. Don't forget the alternator - the brushes can wear out by 120K miles.

I took another listen with the stethoscope. All of the belt driven accesories are relatively quiet running with the exception of the air pump. However, the noise definitely sounds as if it coming from the rear of the engine compartment. Also, the noise is definitely loudest on the transmission dipstick.

The reason I believed the transmission pump was the failing part was because it does "whir" in park. Does the pump not spin when the transmission is not engaged into a gear? Would belt driven accesories change the sound when shifting from park to reverse (more than would be appropriate with the rpm change)?

As a diagnostic step, can anyone advise as to the wisdom of running the car with the polybelt removed?

How would one check if the Bendix gear is not disengaging?

__________________
Kyle Fitzpatrick
Materials Engineer

1969 300SEL 6.3
1992 300E
1994 E320 Touring

I don't think it's a problem running without a belt for a couple of minutes with a cold engine.

Sixto

From your description of the noise it sounds like a plugged filter. Did you personaly see the filter being changed, if the answer is no, change the filter. The pump turns when the engine is turning.