So I have another issue, I have a 01 mustang v6, 190k on the odo. Everytime I drive the car I hear a squeaking coming from the engine bay (not a serp belt, I know what that sounds like) It sounds kind of like a bad pulley (like something is spinning and squeaking) but it doesn't happen at idle, or when I rev it when its in park or neutral, only when I'm in drive and driving, it constantly squeaks and even gets louder for a second every time I hit a bump. Could this be a loose pulley? Which pulley is more likely to go out first? Any other things to check?

 

Also, when I start the car it squeaks but goes away after a few seconds until I start driving.

 

Pull your belt off and give every driven accessory a spin by hand. You'll find a bad bearing right away. Usually the belt tensioner pulley bearing will go first.

 

Awesome, I'll do that asap. Thanks for the help.

 

So I took serp belt off and spun the pulleys. Most pulleys, when I gave them a hand twist, they had somewhat of resistance and slowed steadily to a stop after maybe 3/4 of a spin. But the idler pulley spun freely very fast and made somewhat of a light grinding noise (like the sound of a skateboards wheels rolling down the street). Not nearly as loud as the squealing noise I here while driving. Is this pulley good or bad?

 

I'd say it's bad, it should spin freely with almost no noise. They are fairly cheap and easy to replace. I'd start with replacing it, but it's hard to diagnose a noise over a forum. Good luck and post back if that fixed it.

Edit: After reading your first post, are you sure its not the belt squealing. You said it goes away after a few seconds. A bad bearing will only get louder in time.

 

Now, the noise is quiet on start up and gets louder and louder the more I drive and warm up the car, I can hear the squealing at idle and when driving, it goes with the sound of me accelerating like the squeal is getting faster. And even gives an extra squeal when I got a bump.

 

OK, I'd put my money on it being that bearing then.

 

Cool, imma change that today, it's only like $25. Thanks for your help!! Let you know if noise goes away after.

 

So before replacing the pulley I learned a trick about wd40. I sprayed each bearing on the ac pulley, idler pulley, and tensioner pulley and noise is still present. Again, it's a light squealing noise, heard quietly and sometimes never at idle and noticeable when driving. Mostly happens after car gets warm. So if it isn't the belt or pullies, what else could it be? And also, I can here it when I'm sitting in the car, but when I check under the hood, the engine noise is too loud so I cant pin point it. 😤