Serpentine belt slips

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Serpentine belt slips

Postby missiondevildog » 08 Apr 2013, 17:53

We have an M1123 that the serpentine belt keeps slipping. We've replace the belt numerous time and still the same issue. We also replaced every pulley on the truck as well as the belt tensioner but still keeps slipping. We made sure that every pulley were aligned which they are. When putting on a new belt it will stay on for about the 10 minutes, then begins to slip. But when we turn the truck off the belt slips back into place. The only thing that we can think of is that the crankshaft pulley is missing the mud shield i think its called. it creates a lip over the front of the pulley. Not every HMMWV has it, but ive seen it on several of them. We cant seem to find it in any of the TM's. If anyone can give me some advice on what might be causing the belt to slip or where to locate the mud shield, that would be great. Thanks
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Re: Serpentine belt slips

Postby SUPERMOD » 10 Apr 2013, 16:09

a couple things to look for:
1. though i know you said you checked the allignment, i would double check on the powersteering pulley and more importantly, the bracket on the alternator. If either of those are angled at all, then it will cause a slip
2. where does the slip start when you are watching it?
3. are there any unbalanced pulleys? does the engine shake? (mounts)

let us know thanks.
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Re: Serpentine belt slips

Postby missiondevildog » 14 Apr 2013, 21:42

We have the alternator bracket on order right now. so waiting on that to come in. We also looked up the TI for the pulley alignment and are having the tool fabricated for us. The belt at first was slipping from the idler pulley located above the belt tensioner. I took it off and added a washer to the back of the pulley. This caused the belt to stop slipping from the pulley. But now it seem to be slipping from the crank shaft pulley and the fan pulley. And again it will slip back into place when the truck is shut off. will keep you informed once we get the bracket and tool in.
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Re: Serpentine belt slips

Postby SUPERMOD » 16 Apr 2013, 11:25

good update. when you get the parts in, remember to take off that additional washer before you test it... just in case it works properly without any mods. good luck
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Re: Serpentine belt slips

Postby Petz » 15 May 2013, 11:02

Make sure you have the right belt tensioner on. If you have an ECV tensioner on when it's an 1123 you'll have issues. Also, make sure all the bolts are tight on your bracketry for the alternator and what not. If you have the 400 amp upgrade make sure the bolts didn't break (they do that a lot) which will cause the belt to misalign.

Don't go adding washers behind pullys, you're only hiding the real issue which will eventually grenade on you in the future. find that problem now and fix it!

I've always had loose bolts on the alternator bracket to the engine be an issue. When they break off it's hard to notice but it will cant the pully and cause this to happen. You may also have a bad water pump...

Best course of action is to take the belt off and wiggle all of your pullys, even try a pry bar to see if they take a lateral load without moving. Good luck and let us know what you find.
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Re: Serpentine belt slips

Postby SgtCathers » 25 Mar 2016, 22:56

Just to add another possible solution, look at the alternator bracket. If you have a vehicle with a remote power steering reservoir you'll see two holes in that front bracket that lines up the alternator. Make sure it's in the correct one.
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