Serpentine Issues

I have a '90 XJ and recently had to change the serpentine because the inner most rib had somehow come off the belt. I installed the new belt and now whenever I start the vehicle the belt slips one rib off of the Crankshaft Vibration Damper. This surely is the cause of the belt being previously damaged. I have tried adjusting the belt many times and it continues to slip. Any dvice would be greatly appreciated.

Your Crankshaft Pulley (Harmonic Balancer)has started to separate. There is a rubber piece between the inner and outer part of that pulley. You will need to replace it. Check the old archives for how to.

I think XJ_MAC is correct. On mine the outer rim of the harmonic balancer migrated aft and ground through the timing cover. If you look at the balancer, the rim should be flush with the front of the hub. I think the rim can migrate in either direction when the rubber goes bad.

yes, it is your harmonic balancer, get it to the shop tomorrow to have it fixed.