Chevrolet Repair: cavalier noise, chevy cavalier z24, 1998 chevy cavalier z24

Question
1998 chevy cavalier z24 DOHC 2.4L stock(intake only upgrade) I am in school to become a service tech so i will be able to better understand then most. I was driving at highways speed (110 km/h)and this noise just kicked in (not a squeal, more of a mechanical sound). First thing i did it take the belt off and start it, sound was gone. The belt had little cracks in it(only been in there for a month, but bad quality). I put that belt back on, now the noise only comes at 3000 rpm  and goes at 3500 rpm. Next day i changed the belt to something a little better, no change. also unplugged alt when running(rev to 3000) and all pulleys look good and straight. I don't wanna replace anything without being share what it is. I cant ask at school because i'm out of school for a week and would like to fix it now.

Thanks for your time'
Brad

Answer
Hey,

 That weird zinging noise that is coming and going with RPM is an idler pulley bearing most likely.  You can try and narrow it down with a stethoscope or take the belt off and see if there is any lateral play (side to side) in any of the pulleys.  They plastic idler ones with the bearing inserts are common for failure.  Be carefull when doing this but sometimes you can feel it if you take a 1/4 or 3/8 long extension and put it on the bolt of the pulley.

Waye