Originally Posted by AlanAZ
Take the belt off, and spin the pulleys by hand, you can tell if they're shot or not (watch the videos on the previous page.)
In the video, the guy shows how the bad pulleys free wheel spin and also have a grainy sound.
What if you have just a idler pulley that free spins? Meaning if you rotate it, it spins without any resistance? It doesn't make that sand grainy sound. Is it still bad?
I'm trying to diagnose a sound from my car, not sure what's causing it or exactly where it's coming from.