HMMWV Serpentine Belt Issue - 6.5L

One thing to remember is once a belt is damaged in any way it will continue to jump grooves whether the pulleys are correctly aligned and all the bearings are good or not.

What version of serpentine do you have? Post a pic…
it doesn’t take much for jump off to occur…I’ve dealt with this numerous times with varying reason for it, but all obviously an alignment issue not visible to the naked eye. The one I fixed last week was the Generator/PS bracket was held on with 1 bolt, 1 broken bolt still in the head and 1 missing bolt. The week before that, all 3 bolts on a truck were finger loose, you could see the generator moving way to much while at idle.

Retiredwarhorses said:

What version of serpentine do you have? Post a pic…
it doesn’t take much for jump off to occur…I’ve dealt with this numerous times with varying reason for it, but all obviously an alignment issue not visible to the naked eye. The one I fixed last week was the Generator/PS bracket was held on with 1 bolt, 1 broken bolt still in the head and 1 missing bolt. The week before that, all 3 bolts on a truck were finger loose, you could see the generator moving way to much while at idle.

Click to expand...

Okay I believe I found the problem.

I purchased/installed a Micro-V 25-081264. After 20 minutes, belt climbed rearward on the sandin pulley by 1 rib. The serpentine version I have is:



I believe when my last belt tensioner blew out of the spring housing, the pulley flopped to the passenger side and 'super tensioned' the belt for a period of time. When this occurred, it bent the Sandin unit BARELY inward, canting the pulley forward and more towards center. This is NOT visible w the naked eye. Literally had to use a laser level propped up on a ladder to see the pulley was precisely 1 rib out of alignment w/ the rest of the pulleys. My options seem to be either (a) bend the sandin bracketry back slightly outward OR (b) use a series of washers in the mounting bolts to push the sandin back to the correct position.

I think path of least resistance is to uninstall belt, keep laser mounted as visual reference and install washers to push the sandin unit back out to proper alignment. This should take 2 washers on two mounting points and 1 washer on another. WE WILL SEE! I'll keep you guys posted.

Super interesting. I bet this is NOT in the TM’s.
Nice detective work sir.

TOBASH said:

Super interesting. I bet this is NOT in the TM’s.
Nice detective work sir.

Click to expand...

No, but the drawings to build a pullet alignment tool is.

If the bracket is bent, doesn't that also mean it's no longer square to the rest of the pulleys?

lpcoating said:

If the bracket is bent, doesn't that also mean it's no longer square to the rest of the pulleys?

Click to expand...

The pulley was bent inward, shortening length of required belt and putting the Sanden pulley out of alignment or square w the rest of the pulleys - just barely.

ALSO - SUCCESS!!

Two washers in two of the upper mounting points, pushing the Sanden rearward. Two washers roughly = 1 rib.



I loosened all mounting bolts, removed the two upper bolts, inserted 2x washers/ea then retightened.

As you can see before the fix, the pulley alignment was, visibly, almost perfect. Just BARELY off - when using a laser. The pic isn’t the best, but you can see nonetheless, the belt has climbed one rib.



So far, it’s be idling for 20 min w and w/out AC engaged. No change. Looks solid so far!

Will keep the thread updated.

phemer said:

The pulley was bent inward, shortening length of required belt and putting the Sanden pulley out of alignment or square w the rest of the pulleys - just barely.

ALSO - SUCCESS!!

Two washers in two of the upper mounting points, pushing the Sanden rearward. Two washers roughly = 1 rib.

View attachment 859656

I loosened all mounting bolts, removed the two upper bolts, inserted 2x washers/ea then retightened.

As you can see before the fix, the pulley alignment was, visibly, almost perfect. Just BARELY off - when using a laser. The pic isn’t the best, but you can see nonetheless, the belt has climbed one rib.

View attachment 859657

So far, it’s be idling for 20 min w and w/out AC engaged. No change. Looks solid so far!

Will keep the thread updated.

Click to expand...

Why does that pulley look wider than the belt ? And have more and skinnier grooves than the belts ribs?

Action said:

Why does that pulley look wider than the belt ? And have more and skinnier grooves than the belts ribs?

Click to expand...

Possibly bad picture? I assure you it’s correct.

phemer said:

Possibly bad picture? I assure you it’s correct.

Click to expand...

Ah. I think the high and low of the grooves look the same (white) making this look like 3 exposed grooves e
.

I have been dealing with the same with belts jumping then failing. I had my water pump and harmonic balancer crap out as well, both needed to be replaced. What I see on mine is that the power steering pump is to far forward. The AC condenser is about a half grove off.

Anyone else see alinement issues with thier power steering pump?

avman said:

I have been dealing with the same with belts jumping then failing. I had my water pump and harmonic balancer crap out as well, both needed to be replaced. What I see on mine is that the power steering pump is to far forward. The AC condenser is about a half grove off.

Anyone else see alinement issues with thier power steering pump?

Click to expand...

on my truck it once appeared that the power steering pump was out of alignment.
What it turned out to be was the rear bracket that secures the generator to the engine (on my truck it went to an exhaust manifold stud)had the exhaust stud broken off,a broken gen/PS bracket bolt, and the last 2 bolts loosening up.
Replaced the rear bracket and exhaust stud, only to have it happen again a couple thousand miles later.
Upgraded to the newer style bracket that goes down low on the block instead of the exhaust stut, and upgraded the bolts in front to a higher strength bolt.

No issues since.

Check to make sure all the bolts are good and tight (one of which can pretty much only be accessed from underneath the truck as it's behind the power steering pump) and that the rear mounting bracket is secured properly. That rear bracket has a surprising amount of force on it with the serpentine belt system.

Discussion about it here:

Thanks for the info. I will be climbing underneath today..

Wow - Makes sense w/ the bracketry. In the event you do have to negotiate the issue of bent brackets, which i would view as a can of worms in trying to bend back correctly, I would suggest great care w/ figuring out exactly how much each accessory pulley needs to be spaced inward or outward. Even w/ the use of a laser, I was barely able to see my AC compressor was off by 1 rib (2 washers). Kept throwing the belt on that pulley by exactly 1 rib (which will shred the belt). Knock on wood, but mine is still holding.

avman said:

I have been dealing with the same with belts jumping then failing. I had my water pump and harmonic balancer crap out as well, both needed to be replaced. What I see on mine is that the power steering pump is to far forward. The AC condenser is about a half grove off.

Anyone else see alinement issues with thier power steering pump?

Click to expand...

The condenser has a belt?

Mogman said:

The condenser has a belt?

Click to expand...

*compressor lol

It would be hard to bend a bracket for the AC compressor. The alternator and power steering bracket is cast so it would on crack.

I checked all my brackets and everything seems secure. The attached picture is the alternator bracket bolted to the manifold. it seem there is a washer and nut to hold on the exhaust manifold and then the alternator bracket which is washer and bolted. Does this look like everyones truck? Any recommenation on how to adjust the power steering pump?

I did not realize the power steering and alternator use the same bracket.

I do not understand your question, you do not adjust anything on a serpentine belt the spring loaded idler does this.
If there is an alignment problem then there is something installed incorrectly or bent, ether fix the incorrect mounting of replace the bent parts.

avman said:

It would be hard to bend a bracket for the AC compressor. The alternator and power steering bracket is cast so it would on crack.

I checked all my brackets and everything seems secure. The attached picture is the alternator bracket bolted to the manifold. it seem there is a washer and nut to hold on the exhaust manifold and then the alternator bracket which is washer and bolted. Does this look like everyones truck? Any recommenation on how to adjust the power steering pump?

I did not realize the power steering and alternator use the same bracket.

Click to expand...

even with the stud/nut still sitting there, the stud itself can shear between the manifold and that nut.
It's easier to inspect it for that from the top.

part of the issue on mine was that the exhaust manifold flange wasn't machined flat, so the stud would bend to the side as it was tightened down, creating an uneven stress. Hard to tell in the pic but yours might be similar.

Remove the serpentine belt, then see if there is any movement at all with the generator. It should be rock solid on there. If you can move it at all then there is something not right.

Guys, I’m sorry if this is so basic ))) but I just bought a M1151A1 and a new serpentine belt, which I can’t install it ! Even if I go around the fan blades I hit the engine support bar…. Any advise? (Looked for all kind of videos and couldn’t find any for the M1151….