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Serpantine belt jumps off

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Old 02-18-2013, 02:53 PM
fuelhog450 fuelhog450 is offline
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Serpantine belt jumps off

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?
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Old 02-18-2013, 05:42 PM
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How's your bearings? Any slop in the water pump, alternator, etc?
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Old 02-18-2013, 06:48 PM
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Everything is tight. The truck only has 80,000 miles on it.
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Old 02-18-2013, 08:40 PM
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Nuthin huh?
Bigass washer?
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Old 02-18-2013, 09:12 PM
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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?
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Old 02-19-2013, 07:37 AM
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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.
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Old 02-19-2013, 07:54 AM
fuelhog450 fuelhog450 is offline
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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.
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Old 02-19-2013, 01:04 PM
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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.
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Old 02-19-2013, 01:12 PM
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Can't find it. Maybe the 1994 already had it?
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Old 04-13-2013, 03:58 PM
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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.....
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