Serpentine belt problem

Sounds like something is not installed right. Sure you have the belt routed correctly?

Is something bolted on at an angle? Bracket on wrong?

It's not the water pump, that would leak if not firmly attached.

Your belt may no longer be fitting after all you've replaced. Check your belt tensioner to see if the tension is still within range. You may now need a different size belt.

Check that the new pulley fits your belt and that ALL pulleys are aligning with each other. If one pulley is a little off that will be enough to throw the belt off. Also check that all pulleys are still tight and not a little loose.

check the condition of the rubber on the crank pulley.