ok, so my truck has had a rattling noise since i recently bought it, but i figured it wasnt a big deal since truck was running pretty good. so, im driving down the road and all of a sudden the power steering belt comes off. so, a friend put the belt back on and we drove truck home. he doesnt know a lot, but he thinks he does, so he says he tightened the pulley and put belt back on and thought he had it fixed. i had a feeling it wasnt, so i wouldn't take truck outta town, just drove it about 10 miles probaly before belt came off again. i noticed the rattling noise got somewhat louder more i drove it. so, i dont know if i need a pump, or could the pulley be bad or ?

 

I don't know what belt setup you have but if the belt is also wrapped around the water pump pulley (and it probably is) then that's where I'd look. A rattling is usually the sound of the WP bearings going bad, and failure is just around the corner. Spin the pulley with your hand while the belt's off. If the WP shaft/pulley is loose and/or rattling, there's your problem.