M103 fan clutch Noise?
 

I'm trying to diagnose a loud noise that developed all of a sudden yesterday. I suspected the fan bearing had gone bad/dry and started making noise, so I took the fan off tonight to check it out. Without the fan on it, it spins freely and makes no noise. Everything else seems to spin freely w/o any noise as well.

Now I'm wondering if the fan clutch is the culprit? Are they known to make noise when they go bad?

When I was driving it home yesterday, the noise was bad at idle and low speeds, but almost seemed to go away at higher speeds. I didn't drive it long enough to really confirm that though. Just wanted to get it home and park it...

Pic of the front of the clutch is attached.

Bearing bracket noise? w124
 

Update: I put the belt back on and ran the engine w/o the fan. Noise still there. Clutch is ruled out. Now I'm back to thinking fan bearing bracket. It does spin freely w/o the belt on it, but maybe at higher speeds, under tension of the belt it makes noise?

I guess it could be idler pulley as well...

What does the noise sound like? Is it a grinding noise or something that sounds gritty.....like roller skates over a sandy pavement? Or is it a squeaky sound?

noise description
 

It's hard to describe, but it is definitely not squeaky or high pitched. It's somewhat inconsistent as well--louder at different RPMs.

I went ahead and ordered the fan bearing bracket and the idler pulley so we'll see if that fixes it...

usually if it's the fan bearing bracket...you can wiggle the fan and get some play

Another thing you could've done was put the belt around each pulley component individually and pulled the belt creating tension while working it back and forth to see if you could get it to make the noise.

The one thing that is odd - you say that you can spin the fan easily when off the engine? thats impossible to do unless the clutch was dead - the fan clutch bearing has a lot of drag on it when the clutch is not spinning as the outer race of the bearing is sitting against the clutch case and in stopped condition silicone oil is sitting at the bottom which causes the clutch to be engaged. (thats why the fan works for a few seconds after startup)

fan pulley and bearing
 

That was probably just poor wording on my part.

I removed the fan/clutch assembly and set it aside. With the pulley still bolted to the bearing bracket (after removing the belt) it spun freely and didn't appear to make any noise. Same for the idler pulley, alternator, etc.

After that, I put the belt back on and ran the engine for a minute or two without the fan bolted to the pulley, and the noise was still there. That's what makes me think it's not the fan clutch.

The fan clutch does kinda look like it might be weeping a little as there's dirt build up sticking to the residue on the front... I'll replace it too just in case.

The alternator was new about 3 years go, so I'm hoping it's not the culprit, although the noise is in that general area - kinda near the fan bearing/idler/alternator...

True, and there doesn't seem to be much play there. Makes me wonder.

I took video of it making the noise, but it's hard to hear when you're not there...