We had an issue with a serpentine belt splitting. In fact, it happened with two or three different belts. Took the Expedition to a Ford dealer and they found a very small piece of rock embedded in the grooves of one of the idler pulleys. When the belts were changed, no one ever noticed the rock, so it kept destroying belts.
Old belt was in good condition and I changed the tensioner the new belt was making an old squeaking noise but it seemed to be just at certain times so figured the back side where the label was or maybe just because or was brand new. Old belt is back on and if it lasts more than 50 miles the new belt had a defect. And I should say the new belt literally exploded. Will get a picture later on when I am out of here.