High pitched whistle

[pegdrag]

2002 LC which I gave to my daughter in law. All baselined, just did new serpentine belt because of some slipping. There was an easily heard whistle before the belt replacement which went away post new belt and careful adjustment.

The truck now has a faint and inaudible to me whistle on start up which lasts 3 or so minutes and then stops and never re-occurs until the next cold start. Occurs with car sitting still.

It is hard for me to troubleshoot because I can't hear it. My son can hear it, but it is only faintly audible to him.

Water pump, radiator, thermostat are all about 1.5 years old. My daughter in law is apologetic, laughing. Says "Dad, I'm sorry, but its still there."

I'm tempted to ignore it, but......Any thoughts?

PS telling my daughter in law she is crazy won't work....she isn't.

 

[ZG MN]

Maybe power steering pump?

 

[Mike NXP]

We can play the guessing game all day long but if you suspect the noise is coming from a belt driven engine accessory you'll need to diagnose further.


Curious how you determined your belt was slipping and what you mean by "After slight adjustment"? These belts are self tensioning so what did you adjust?

It also should be said that belts and pulleys spinning will make some noise, if you can't even hear it, it doesn't sound like it will leave you broken down anytime soon.


So diagnose it a bit further,
First step, take the belt off and then start the engine. Keep your fingers crossed and hope the noise goes away
>> If the noise doesn't go away you may be dealing with a timing belt driven component.
>> If the noise does go away then you can narrow down your suspects by spinning some pulleys.


They should spin smoothly with a bit of resistance. If they just free spin along like a skateboard wheel they need replacement. Check belt tensioner for proper spring back tension. Spin your fan, AC , and Alternator pulley. Maybe even engage the AC when the belt is on and see if the noise changes.

Just need to try and narrow it down, until this is done you will just be guessing and throwing parts at it.

 

[pegdrag]

We can play the guessing game all day long but if you suspect the noise is coming from a belt driven engine accessory you'll need to diagnose further.


Curious how you determined your belt was slipping and what you mean by "After slight adjustment"? These belts are self tensioning so what did you adjust?

It also should be said that belts and pulleys spinning will make some noise, if you can't even hear it, it doesn't sound like it will leave you broken down anytime soon.


So diagnose it a bit further,
First step, take the belt off and then start the engine. Keep your fingers crossed and hope the noise goes away
>> If the noise doesn't go away you may be dealing with a timing belt driven component.
>> If the noise does go away then you can narrow down your suspects by spinning some pulleys.


They should spin smoothly with a bit of resistance. If they just free spin along like a skateboard wheel they need replacement. Check belt tensioner for proper spring back tension. Spin your fan, AC , and Alternator pulley. Maybe even engage the AC when the belt is on and see if the noise changes.

Just need to try and narrow it down, until this is done you will just be guessing and throwing parts at it.

I'm not terribly suspicious that it is the belt. Pulleys all seemed fine. The belt was worn and replacing it got rid of the original whine. You are right, there isn't really an adjustment for the belt. Perhaps should have said "after installation per FSM".....

You are correct, I do need to pull the belt and recheck.

What is odd about this is that the faint noise goes away in under 3 minutes.

Tensioner bearing? I'd expect that to get louder, not disappear. I also wondered if it was some alternator noise.

I'll plug away at it....but was hoping for an quick and easy diagnosis from you more expert fellows.

Appreciate the responses, however.

 

[Mike NXP]

I'm not terribly suspicious that it is the belt. Pulleys all seemed fine. The belt was worn and replacing it got rid of the original whine. You are right, there isn't really an adjustment for the belt. Perhaps should have said "after installation per FSM".....

You are correct, I do need to pull the belt and recheck.

What is odd about this is that the faint noise goes away in under 3 minutes.

Tensioner bearing? I'd expect that to get louder, not disappear. I also wondered if it was some alternator noise.

I'll plug away at it....but was hoping for an quick and easy diagnosis from you more expert fellows.

Appreciate the responses, however.

Don't use my experience to help diagnose but I've been battling some high pitch bearing whistle noise as well for a while now. Fast forward 2 years and I have replaced just about every belt driven part and it's still there. (The last part I haven't changed is the actual AC compressor) It won't leave me broken down so I have moved on for now, until it gets louder and screams at me to fix it.

As for your diagnosis, you can get a handful of guessing from the forum but unfortunately it will require you to get in there and check all components. It's not that strange that it goes away once warm, the cold seems to bring out all the squeaks and creaks. Maybe it's as simple as a bad idler pulley.

Does it happen consistently when cold? I'd say first step is pop the belt off and start the motor ( when cold ) and hope the noise goes away. If it does you can focus your attention on the serpentine belt driven components. Make sure pulleys are clean, spinning smoothly, tensioner is springy, etc. etc.

Report back if you need more info / find the problem.

 

[planomateo]

Air injection pump was my first thought, but don't think an 02 has that system.