I place stethoscope on the bolt holding in the idler pulley. Same on tensioner pulley. That is best done when cold, but generally I still hear chirp with it, after warm up too.
When you remove the belt spin pulleys like in my video above. Then you'll know for sure which are bad. Typical they are both bad.
When you remove the belt spin pulleys like in my video above. Then you'll know for sure which are bad. Typical they are both bad.