So i went to jumpstart a buddy and when i popped my hood i heard the most god awful noise coming from my alternator. It isnt a constant sound however its almost rythmic. Like off an on, sound like a knocking/grinding accompanied by a slight squeal (very very slight)

i held my hand on the alt and when it made the noise it vibrated so im 99.9% sure its that or the belt tensioner next to it.
i just want someone elses opinion
what is failing?
how detrimental is it?
and most importantly am i right?
( i dont have a belt over the ac pump or power steering…)

 

Pull the serpantine belt off. Spin the altnerator by hand. See if it feels anything but smooth turning. Same for tensioner. Check for play, try and wobble the belt tensioner pully.