Noticed it was very loose at work but not enough to fall off.

Decided to drive home and fix it since I didnt have tools

Got home and during the whole way sounded like a kid dying.

Popped the hood and the belt is tight and no play.

Belt is very hot.

Only drove 7 km home.

Smoking from alternator pulley area.

Now it won't stop squeeling and the belt is tight. Should I replace it anyways since I have the part ?

 

Pull the belt and make sure the alternator isn't seizing up.
Belts don't normally go from too loose to too tight by themselves.

 

Bad alternator bearing or loose air pump belt making the alternator belt work too hard to turn the water pump.

 

Will a Turbo alternator from an s4 work on any s4? I heard they are interchangeable

There is no slack at all now. I'm stumped. Pully is hard to to turn on the alternator.

Still doesn't explain how the slack went away since it can't go farther up since I have the strut brace.

 

Also I spun the alt freely its not super smooth but it goes. Also it ticks when spinning counter clockwise unlike my replacement Turbo alt.