just installed new water pump and belt on my 2000 Cherokee . When I start it the belt squeals for a few seconds . What did I do wrong ?

 

Presuming u loosened the adjusting idler pulley to remove the old belt, it sounds like the new belt needs to adjusted a pinch tighter.

 

Most likely that....or a dirty belt...

 

djb383 is on the money. With a new pump/belt, it is not unusual to have to tighten the belt after running it for a few minutes.

In fact, I have had to do this every time I changed the belt on my 99.....Even good quality belts "stretch" just a very tiny bit when under load.

The belt on the 4.0 needs to be awfully darn tight to stay quiet. Tighter than most any other vehicle I've owned. Snug it a bit and I'll bet that noise is gone.

 

Try 1/2 turn on the adjusting bolt at a time. Be sure to loosen the idler pulley 1st, then turn the adjusting bolt 2nd, then re-snug the idler pulley 3rd. Still squeaks, try another 1/2 turn adjustment.