Help! Possible noise from fan on M104.
 

Over the weekend I noticed a strange sound coming from the engine.
It only happens when the car has been warmed up and driven around.
Temperature in the 95 degrees area.
Hard to explain the actual sound but kinda sounds like a rattling/grinding sound.

The sound does not change with the RPM of the engine. Nor does turning the AC on and off have any effect on it. When I stop the engine, the sound will continue for a few seconds and stop. I think it may be related to the fan but cannot be 100%. Also, when the engine is off, I tried turning the fan blade to recreate the shound but it doesn't.

Does anyone have any clue to what it could be?

BTW, it's a 96 E320 inline 6 with 169K miles.

People far more knowledgable than me will respond, but here's a thought.
The fan is mounted to a bearing bracket. Those bearings can go bad.
The bracket is about $170 bucks or so.

Steve

Are you sure it's the fan? on my M104 there's a rattling sound from the area of the fan, turned out to be the idler bearing pulley.

Use an old stethoscope (or similar) to try and trace the source of the noise - beware of moving belts while the engine is running.

One of the few mechanical things that may still turn after the engine is shut-off is/are the fan(s) as well as the auxiliary fan.

Next time while the noise is still there have someone turn off the engine and watch the fans. See if they are turning, and if so determine if the noise stops as soon the the fans stop. You will then know if that noise originates from the fans or not.

If it is this bearing, is it easy to replace or will it require moving/removing of the radiator?

I tried that, the fan blade will still move when the engine turns off but the sound stops after a sec even though the blade is still turning. I tried to turn the blade with my hand to reproduce the sound but it would not.

Anyone else have any ideas?
I hate to throw in the towl and take it to a dealer.

Any chance you can record the sound and post it. It will be much easier to diagnose remotely and will eliminate guess work.


Phil

Well, my update on this problem is that I think the problem went away.

I was driving home and I took a sharp turn at about 45MPH.
The check oil light came on. This has never happened to me on this car.
So after I got home and let the car cool down, I checked the oil. It showed half way point on the dip stick. I was confused as why the light came on. I have had the oil at mid point before and never had the light come on. I thought maybe the check engine light came on due to my sharp turning. So I put in about half a quart of oil and topped it off. Since then, the sound has disappeared.
I am not sure if the oil has anything to do with it but the sound is gone so I am hoping that it will stay that way.

But I just can't imagine that the oil has something to do with it.
Could my problem have been that simple?

Probably not. How long does the sound go on for when the engine is off? Not a lot of moving parts that could make that noise with the engine off.

One thing to check is to remove the fan and the serpentine belt, and spin each pulley by hand. Listen for roughness or noises from each of the pulleys, common problems include the idler pulley bearing and the fan clutch bearing.

That is exactly what I did when I replaced my water pump on my 104. I spun every pulley. I had to replace the alternator, and the idler, and the tensioner, they felt rough when I turned them, not smooth. You can just remove the belt to do this. Good luck.
brian