I am having a problem where the serpentine belt will slip off after short periods of driving. The belt brand new will come off after say 200 to 300 miles. It first started after I had the engine replaced with a used one. Van motor is a ford 4.9l inline six. What could cause this? Since I have replaced the tensioner pulley, starter and smog pump. I use the van for work and have been burning through belts been under the hood more than enough times. Thanks for any replies

 

get a straightedge and check the alignment of your pulleys, one is probably off a little, or is bent and wobbling.

 

Ok, If off how would I adjust? Washers. I think all pulleys are spinning straight I'll check again

 

Assuming all the pullys are in alignment,I think you may not have enough tension on the belt. Tighten it up.

 

Do ford's have tensioner pulleys? If so that might fix s***

 

They do I think i'm going to replace again maybe defective.

 

wow i guess i should have read a little more closely, oh well, good luck with your belt