135i N55, Pulley or something more serious?

[Aver]

So today I wanted to check my car since i didn't drive it for a few days so i turned it on and this is what i heard is it just a pulley going bad or worst case scenario?

[olds350]

Hard to tell, but sounds like a bad idler pulley. Best way to check is with either a long screw driver or mechanics stethoscope. With the motor running, CAREFULLY place the end of the scope on the retaining bolt. You'll hear a very distinct sound difference when you hear the bad pulley...

[Matticus91]

Hard to tell through video audio but could definitely be the pulley. Fairly easy job and not too expensive, I'd try that first unless you have a shop you can trust.