I replaced the power steering pump on mt 2000 montana and it keeps throwing the belt off..why?

That has the big serpentine belt and a tensioner. Check the tensioner and the idler pulley.

Do you have the pump drive pulley off yet?
Remove the drive belt, remove the 3 mounting bolts (15mm) by using a socket ththrough the holes in the drive pulley. Remove the upper intake manifold to give elbow room, slide off the rubber return hose, remove the pressure line and lift out the pump. Just reverse the process to instill the new pump. And fill with the proper fluid.

Remove the drive belt, remove the 3 mounting bolts by using a socket ththrough the holes in the drive pulley. Remove the upper intake to give you room, slide off the rubber return hose, remove the pressure line and lift out the pump. Just reverse the process to instill the new pump. And fill with the proper fluid.

You need a special tool, go here to see one. Local it will be much more likey.

Check to see that no bolts or mounting brackets are loose causing the power steering pump to be out of alignment with the rest of the pulleys. When replacing the belt make sure it is seated correctly on the pulley because if it is one ridge off it will cause the belt to shred very quickly.

Remove the belt, there are 3 bolts that you have to remove through the openings in the pulley. Remove the power steering lines from the hold down bracket on the left lower side of the engine then remove the return rubber hose from the steel line by removing the front right tire and splash shield. Then you can lift the pump up and out and have room to remove the pressure line.

check the fan belt to see if its glazed from slipping,if it is you can spray some stuff on it called belt dressing,if yhat doesnt work you will have to adjust it or replace it.

Sounds like your serpentine belt either fell off or broke. Check all the pulleys to make sure they rotate. Wiggle the water-pump pulley to see if the bearings are bad. Check the tensioner to make sure it isn't frozen or worn out. If all those check out fine replace the belt and see what happens.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

check all the bearing in all of the acc. power steering pump water pump idler pully a/c compressor etc. if all good no nise and they spinn freely check the alinment of all the puilly mak so they all line on together. sometimes the power steering pully get worn inside the pump and allow it to move back and forth too much some play is normal. also the power steering pully trys to walk off the shaft and make the belt track off the other pullys .

Hello there: here it is