Diagnosing a bad pulley

[JS1500]

A few weeks ago my truck was making a chirping sound when driving that sounded to me like a pulley going bad. It ended up going away for a while, but now it's back, but it sounds a little different. Rather than a chirp, now it sounds like a cyclic whooshing. I looked under the hood today when the truck was running, and there is definitely an abnormal sound coming from the pulley/belt area. The sound stops after I've been driving for 15-20 minutes. Also, it seems to only become prominent when it's colder than 30* outside. From the research I've done, I suspect that it could be the idler pulley or belt tensioner pulley. The truck only has 40,000 miles, so it seems odd that these components could already be going bad.

 

[navyguy3117]

May sound like an old idea but it works. Take a really long slim flat head put the blade of the flathead on the center of the pulley while it's running and the end of the handle to your ear. You will be able to tell a significant sound difference between the good pulley's and the bad one if that's the case. It actually sound like a work belt to me if it left for a bit and came back.

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[grizzstang]

Or pop the belt off and turn all the pulleys by hand. You will be able to feel and hear the bad one.

 

[2016Bighorny]

Take a long scrap piece of fuel line, rubber tubbing, hose, Ect. and hold one end to your ear and hold the other end by the front of each pulley. This works and is cheap. OBVIOUSLY, be SAFE and keep hands and fingers AWAY from moving components!!!...