SOLVED! New high pitched squeal heard at idle

[Jkb242]

Merry Christmas and best holiday wishes to all and thanks for the participation so valuable here in helping others.
My issue:
My 2006 Denali with the standard issue 5.3L V8 just developed this abnormal sound which first began after a cold start this AM, but cold here means 60F. After a normal start, the high pitch was pulsing about every 750ms and continued steadily until it finally assumed a constant squeal. The squeal was not loud and would likely be un-noticable in the car with the windows up. With the hood open standing directly in front of the engine bay it was unmistakably noticeable.

I attempted to listen with a screw driver coupled to my ear while touching the case of the left most idler but did not detect the squeal there. I could not safely access the right idler using this test with the engine running. The sound appears to be coming from the center like fan clutch water pulley area. I would really appreciate some diagnostic procedures I could try to isolate the source of the squeal.

A) Is it possible to disconnect the fan clutch and start the car to possible isolate any clutch issues?
B) Is it possible to reroute the belt so that one of the idlers is bypassed then start and listen?

I would appreciate any input in this diagnosis before just replacing parts. I'll need this car for upcoming Christmas visiting and would like to take care of this before.

Thanks indeed!

 

[Mooseman]

A) Is it possible to disconnect the fan clutch and start the car to possible isolate any clutch issues?

Yes if you mean unplugging it.

B) Is it possible to reroute the belt so that one of the idlers is bypassed then start and listen?

I doubt that can be done without a shorter belt. However, usual diagnostic technique is to remove the belt completely and start the engine to confirm it's a belt driven accessory. If noise is gone, try spinning each accessory and idler by hand for noise or roughness.

 

[Jkb242]

Thanks Mooseman, yes indeed unplugging the fan, but would that keep the clutch fully engaged or fully disengaged?

 

[Mooseman]

Disengaged

 

[Jkb242]

Thanks again moose man!!

 

[mrrsm]

Pulling the Serpentine Belt looking for edge damage and cracking as well as spinning the Idler Pulley AND the Alternator Pulley and listening for any Whirring or Grinding Noises can be very revealing. If the Water Pump Bearing is "Wobbly" it can induce High Frequency 'Chirping' as well.

 

[Mooseman]

As well as misalignment of the pulleys.

 

[STSCowboy]

Any updates?

 

[Jkb242]

Replacement of idler, and coolant temp sensor seems to have corrected all originally reported issues. Fan clutch and radiator thermostat originally suspects were not replaced as they seem to be working normally.
I should have marked this issue solved. Sorry for that oversight and thanks to all contributors!!

 

[Mooseman]

And Solved!