Fan/WP/Bearing/Belt Squealing Question

[Third From Texas]

It doesn't happen all the time and it only happens just as the temp hits 200 (but several seconds before the fan actually engages). It stops after a couple seconds.

I know the clutch and fan were replaced in this truck back around 2017 and under 4000 miles ago (likely *well* under).

My assumption is that it's a bearing (it's the tell-tale squeal of a dying bearing) but I'm uncertain as to the things I can check when I tear it down. I've read a number of threads and am familiar with the temp switch, solenoid (I just had it apart to clean), and scrolled thru the TM looking for clues.

I assume it's not a bearing on a belt tensioner or anything that would be noticeable at all running times.

The belts *look* to be in order (AC, charging systems, etc all functioning normally).

So I figure either water pump or a bearing in the fan clutch (more suspect of the later do to the timing of the squeal).

Thoughts?

 

[Ronmar]

Well I dont see a bearing being that selective unless it is reacting to temperature.Only bearing I see in that situation is the water pump... The fan bearing is either freewheeling or not. You could disconnect the temp switch and delay the fan coming on a bit to see if you can get the sound to persist long enough to track it down, just watch the temps. Do you have a mechanics stethescope to listen to the various housings/mounts for unusual noises?

 

[simp5782]

If you can get it to do it with the hood raised just keep a can of WD40 when you hear the noise start spraying pulleys till it goes away. I would first Remove your standard air line from the fan clutch and add a line from an air compressor to it to keep the fan from coming on all the time with a constant air supply.

more than likely its in the clutch setup though.

 

[NDT]

I have this issue on a fire dept LMTV. In my case it's the voltage regulator going into spasms sending high current and resultant high shaft loads on the alternator. Check into that also.

 

[coachgeo]

Similar to wd40 idea but opposite direction. Spray belt dressing on the belts. If the squeal stops for a while then you have belt more worn than you thought. Granted a wonky voltage regulator causing increased forces on belts would wear them faster.

 

[Suprman]

The clutches squeal sometimes. Maybe your fan clutch solenoid is sticky. Or your fan clutch is worn. The earlier style fan clutches dont seem to grab as hard as the newer ones.

 

[Third From Texas]

UPDATE:

I reinspected all belts and while the AC belt appeared tight, I was able to tighten it a bit more to my liking. Since AC was a more recent mod done to the truck, it seemed like a good place to start.

Squeal eliminated !

Strikes me as odd that it was materializing just as the temp would hit 200 degrees, but the AC belt does appear to have been the culprit.

Thanks for the suggestions, all. Always happy when it's a simple or cheap fix.