What's going on guys, I've looked through the forum but I couldn't really get an answer. I replaced the belts on my car earlier this week, the car is an 01 C5 stock LS1, everything ran good then the new AC belt snapped so I got it warrantied. Once I replaced it again my serpentine belt keeps jumping back like 3/4 of an inch towards the block. The belt is brand new, I checked the balancer it looks good no cracks the rubber looks good too.. I made sure the belt was all the way on correctly which it was, but I just can't figure it out. Anyone else had this issue before?

 

I had this problem way back when I had my 98 Camaro. Had to replace the tensioner pulley with a high lip pulley from Auto Specialties. Problem solved!

 

Likely a faulty tensioner.