Engine whirring noise

[RussellSullivan]

My 2006 with 116,000 miles on it and manual transmission made an odd whirring noise recently.
It was related to the engie speed as it changed with RPM's. It only lasted a few seconds so I wasn't able to stop and listen closely for it. When I purchase this truck about 5 years ago at 85,000 miles I replaced
the idler pulley, tensioner pulley, fan bearing, fan clutch, and water pump. The clutch release bearing has only 2500 miles on it. All of the above are best quality parts. From Genos or Cummins.
I removed the belt and spun each of the above and listened for roughness and felt for excess play.
All still seemed like new. The alternator turned smoothly with no noise as did the AC compressor.
The power steering pump turned smoothly but has about 1/8" of end play on the pulley shaft.
Is this normal for the PS pump or is the maybe the source of the whirring noise?
Could this be from the alternator already wearing out or from the AC compressor?
I really don't want to have this "go out" a long way from home.
Any help you can offer will be much appreciated.
Thanks, Russell

 

[AEdelheit]

Are you sure it was not the engine fan fully engaging for a few seconds? If you are working the truck harder and in higher temps then you have before it may be that the fan has never had to be fully engaged in the past.

Typically if a bearing or pump is going out the noise starts and will be consistent or get worse not come and go.

 

[RussellSullivan]

No, not the fan. I hear it come on regularly here in our 100 degree plus Arizona days.
I should have described the noise better. It was more like “ zzzzzzzzzzsssssssssst. Zzzzzzzsssssst. Zzzzzzzzzzzzssssssssssssszzzzzssss
More like a dry bearing or something (like a straw) briefly coming into contact with a small high speed fan. Not pine needles in the heater fan though, this time. I will check the alternator for a possible stray object in it. Hope this helps. R

 

[Topzide]

May want to check the belt for any cracks or missing ribs. When running around the pulleys, any belt issue could give you the noise. Had that on a different vehicle. Just a thought.

 

[Ozymandias]

Any difference with AC On or Off?

 

[RussellSullivan]

The two times this happened the AC was on. Once about a month ago and just a few days ago.
Both times the noise was very short, maybe three seconds at most. Definitely changed with engine RPMs.
I will check the belt carefully later today.
Question. Does the clutch release bearing spin all the time on this truck or only when the clutch is depressed?
If I remember correctly, I was pulling away from a stop sign when the noise occured and undoubtedly clutching
and shifting......???

 

[RussellSullivan]

Thank you all for your thoughts. You helped an old guy to think more and ask less. I hope.
In a couple weeks I'll pull the transmission and replace the release bearing.
R