I'm at my wits end with these drive belt issues. The belt doesn't squeal at idle, but squeals most significantly right when you get the car moving. At high speeds, it doesn't squeal. The belt comes off if you accelerate hard to ~50 MPH. I've replaced the tensioner, idler pulley, friction wheel, and AC compressor clutch pulley. All of the pulleys seem to spin freely, don't make any weird sounds without the belt on, and look properly lined up to the eye. When the belt is on, it seems tight and properly tensioned. None of the components have notable play. I've gone through several different belts to see if I had the wrong one, but the Continental 4060352 seems to fit best of all the replacement options that people recommend. What could I possibly be missing?

 

Are you absolutely sure that it's definitely not a bearing in the alternator.....

 

I really don’t think so. It spins pretty freely and doesn’t make any weird noises. I took some video of me spinning the pulleys, what do you think? When the tab is pulled on the idler pulley, both it and the water pump friction wheel spin smoothly.

https://www.dropbox.com/s/t5iwj6kxht..._3486.MOV?dl=0

i’ve also included a photo of the (brand new) compressor pulley because some rubber from the belt has melted down into the cracks. Should this lead me to believe that the compressor might be seizing?

 

That does not look happy if the others look good this one looks suspect?

 

That's definitely not looking good...... do you have the belt properly lined in the grooves when installed.......
with the belt installed and car running you should be able to see and tell what's going on.....I've heard
some crazy sounds coming from a bad friction wheel and bearing from alternator.....

 

What's the best way to determine which component is causing the noise while running? I do have one of those mechanic stethoscopes.

 

that's exactly what you would use...... I'd start it first and see if you hear anything briefly before installing the belt....... Don't keep it running long..
then install the belt and listen for anything sounding weird.

 

The compressor pulley is controlled by a clutch mechanism used to control whether the compressor is running or not. If the clutch is in its "off" position (like when the engine is switched off), then the pulley should turn as easily as e.g. the friction wheel pulley when its release tab is pulled out. In your video, the compressor pulley does not turn freely.

What is more, the rubber inside the pulley's tracks indicates that the pulley exerts a higher than normal resistance when being turned by the belt. Higher than the max. load by the compressor by design. Hence the problem is not just whether the clutch is releasing the pulley or not but that the compressor itself has an issue.

Note: I'm no technician, the above is simply my reasoning. Whatever the cause, I'd scrape off the rubber residue inside the compressor pulley's tracks. But even if this stops the belt from slipping and squealing, it will not address the underlying root cause.

 

Thank you, I’ve replace the crank pulley also now and still have the issue, so I’m pretty confident it’s the compressor. Just had a shop purge the refrigerant so I can swap it out.