3.4 liter - 5vz-fe - strange whirring/screeching sound... Help.

Hey everyone,

Long time visitor, and first time user. I have a 3rd generation truck that started making this noise during our first cold snap in Columbus about 1 month ago. Here is a Youtube video link to the engine and sound.... It is titled:

3rd gen 4Runner - cold weather screech

https://www.youtube.com/watch?v=WimarkAjvak

Here is what I can tell you:

1. All 3 belts are fairly new
2. The A/C idler pulley was replaced 9 months ago.
3. The alternator is brand new
4. The power steering pump is not the culprit - verified by Toyota mechanic.
5. It only does this on very cold days (we have had a lot of them), and ususally after truck has been sitting and engine is cold.
6. The timing belt, water pump, tensioners, etc. were replaced 30K miles ago.

I think it may be the a/c idler pulley again? (I used the

$26 Gates 38031 DriveAlign Belt Drive Idler/Tensioner Pulley

Gates 38031, so it should be OEM quality)
I am thinking it could be the fan cooling bracket?

I have a stethoscope, but cannot totally pinpoint the noise. Any help/suggestions would be greatly appreciated!

 

Check the tension on all the drive belts you can take off the power steering belt to try eliminating moving parts..process of elimination is your key when diagnosing noise issues