Help! belt not the one around my waist

[money pit]

98 vette 30,ooo milles. belt started to shred so I bought a new one and put it on and drove it. Next day, I went out to start it and it threw the belt off.
I went and bought another. When you start it the belt jumps on to the edge of engine pully and rides there. I know that isn't right. Took belt off and on several times, same thing every time . checked all the pullys they seem fine.

 

[Huskerman]

Is your belt tensioner locking up on you......? With only 30K miles you would't think so......14 years though.....

 

[money pit]

Is your belt tensioner locking up on you......? With only 30K miles you would't think so......14 years though.....

moves back and forth smoothly and spins freely.

 

[bill81vette]

one of the pulleys is going bad,you are going to have to determine which one,
and replace it stop it from throwing the belt.

 

[navy2kcoupe]

Check tour belt tensioner. My old one was the one on the left. New one is on the right.
Check it from the passengers side, and watch how the belt rides. Mine was riding forward
on the water pump, and would eventually jump off. I replaced the tensioner and it hasn't
come off since. It now rides dead center on the water pump like it is supposed to.
Andy

 

[Toms007]

I'm thinking Andy is right. You wouldn't think so with just 30K but crazier things have happened.

 

[Hib Halverson]

1) Make sure you're using the correct replacement belt and use a high-quality part such as Goodyear Gatorback, Gates or OE GM.
2) Make sure the best tensioner is in good condition. If the spring tension has decreased that will cause the belt to come off. If you need a new tensioner, use either a Goodyear or OE GM.
3) Check to make sure all pulleys are in alignment.
4) Check to make sure the crank pulley is not loose.

 

[money pit]

belt wtf 30,000 miles

could not figure it out brought it to a dealer $$$$$$$ .answer is harmonic balancer.