remove drive belt and check all pulley wheels for freedom of movement sounds like a pulley wheel is bad, probably the belt tensioner pulley
That pulley has a bearing on the inside of it that has gone bad. Replace the pulley with a new 1
I'm assuming you mean a pulley, which is what the belts run on. If so, depending on which pulley the bearings could be bad or if it is the crankshaft pulley (big pulley near the bottom) the rubber could be getting bad.
Sounds like you need a water pump, The bearings in the water pump are making the noise not the pulley.
Bad bearing in a belt driven accessory? i.e. alternator, water pump, idler pulley, belt tensioner, etc.?
When it goes bad
it's not as bad as it sounds.
In most cases you can purchase the bearing and pulley as an assembly from your local auto parts store.
Serious vibrations.
cause the tensen pulley could be going bad an my need to be replaced or even your alternater pulley can be getting ready to go bad
It sounds like there is a pulley that is bad or the serpentine belt is bad. Try spraying a little water on the belt while it is running, if the nosie stops, it is likely the belt.
The idler pulley has nothing to do with the brakes. If the idler pulley is bad it could throw or break a belt, and then your engine will stop.