2001 4runner: Screeching noise - Need help

[Buoni]

Hey everyone,

Long time visitor, and second 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 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!

 

[gamefreakgc]

I have that exact same noise. Only when cold and when starting up the engine, usually at 35 degrees or colder.

My belts are also good, and I have the dynamic tensioner with the supercharger so I know it's not my main drive belt. My power steering seems a little stiff, so I was going to eventually clean off the pulley and change the belt.

I've never messed with the fan but it might be a loose part. It doesn't wobble or nothing though.

 

[Buoni]

I know it's not the power steering pump or belt...

Am leaning toward the 2 items I mentioned in my post - fan bracket housing (fake water pump), or the A/C idler pulley....

Any expertise on this topic would be very welcome, as I don't want to keep chasing this with more $.

 

[Mynameistommy510]

I wouldn't think it's pulley or belt related since the tone of the sound is changing and the speed of the belts and pulleys aren't.
Could it possibly be the fan clutch? Maybe try out the towel trick with the fan to see if your fan clutch is working properly.

 

[Buoni]

Thanks for the reply -- I should have included that the change in speed/pitch was due to opening the throttle body up with my hand. I was "giving it gas" to show that the noise remains present (different pitch/volume) even when the pulleys are moving at different speeds... Hope that helps.

 

[gamefreakgc]

I wouldn't think it's pulley or belt related since the tone of the sound is changing and the speed of the belts and pulleys aren't.
Could it possibly be the fan clutch? Maybe try out the towel trick with the fan to see if your fan clutch is working properly.

What is this towel trick you speak of? Please elaborate!

 

[Mynameistommy510]

What is this towel trick you speak of? Please elaborate!

With the engine warm, stick the end of a rolled up shop towel in the fan blades. If the towel resistance is able to stop the fan, the clutch is bad.
With the engine off, the fan should have some resistance trying to spin the fan by hand. A free spinning fan is also a bad clutch.