I fail at searching. serpentine belt site: ford-trucks.com/forums/forum117/

My belt jumps off at startup even after:
New belts
new idlers
new tensioners
new tensioner bolt
aligning power steering pulley

What am I missing? It can be months with no issue, then...........
Is there a mod to keep the belt from slipping off the back side of the idler and tensioner pulleys?

 

How's your bearings? Any slop in the water pump, alternator, etc?

 

Everything is tight. The truck only has 80,000 miles on it.

 

Nuthin huh?
Bigass washer?

 

I assume you studied each pulley for run-out while the engine is running? Sounds like you've covered the basics, maybe look closely at each grove in each pulley for damage or wear?

 

Wasn't there a TSB about the serp belts jumping off on these things... I want to say they rerouted the belt and changed a pulley or something.

 

I remember on the ambulances, swapping a different tensioner in with a big damper on it.
I'll get a pic of it later today so you guys can see what it looks like. I can make a short vid of it running too. My belt is all bobbly now. I may have a new one in the garage still.

 

There are two tensioner designs. If you look on rock auto you'll find the tensioner marked second design. Get that and put it on. If you replace a serpentine belt you should replace the tensioner too.

 

Can't find it. Maybe the 1994 already had it?

 

A shorter belt seems to have solved the problem.
All pulleys measured close to spec and are aligned as close as I can get them.
The tensioner is the updated one.
I can't figure out what makes my serpentine drive want a shorter belt but that's what I'm running.
The indicator pointer is where it should be so.....