I changed serpentine belt on 2003 5.4 2 weeks ago. The one there was squealing on cold startup.....sometimes. It had shed one whole rib off belt, only 5 left on a 6 rib belt.

New Gates belt was fine, no noise. After 1000 miles, the new belt self destructed, shedding the 6th rib. This is the one toward the front.

there is no play on tensioner or idler pulley.

the PS pump shaft moves in and out a tad, but not wobble

I figured bad tensioner is normal cause, but I had to use cheater pipe on breaker bar to replace the belt, so the tension...is fine, and theres no pulley play.

??? what else can cause this suddenly

 

Is the AC compressor locking up?

 

AC works fine.

 

Could have been a bad/weak belt from the factory.

 

Are you sure you had ir correctly seated on all the pullies?

 

I dont think it woukd last 1000+ miles if on incorrectly.
It concernung because the previous one had torn off a rib as well, doesnt seem like coincidence.

 

If something came loose, as in the belt isn't completely lined up, I could see it shredding over time You said the tensioner was tight. Are all the mounting bolts on good? This a complete shot in the dark, but my guess is one pulley has shifted slightly for some reason or another causing more stress on one side of the belt. Did the belts wear on the same side?

That's one thing that could be happening. As Tackle said, there is always the possibility of a defective belt from the factory.

 

Wish i had paid enough attention to the first one to know if was the same. it had 100,000 mi or so. Maybe something only flex under belt tension and load but feel tight by hand?

 

Inside rib or outside ?