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Old 19-02-2024, 09:07   #1
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Pulley alignment; serpentine belt dust

Hello, I have a Universal M35-B with the Balmar Alt-Mount serpentine kit and I've been trying to diagnose what feels like excessive belt dusting to me. I was under the impression that serpentines should have very little if any dust, but mine will gather rather dense "dust clumps" near the pulleys after a few hours of engine time.

(I know I might get flak for putting my fingers near a running engine but I was wearing safety glasses

I used a straight edge along the 3 pulleys and had a machinist make shims to get the pulleys aligned within a very close tolerance, and I used a belt tension tool to adjust the belt deflection to 1/2" under 25 lbs.

Next I wanted to see if the pulleys themselves were rotating properly, so I used a radial dial on the outer edge while they were spinning: the water pump and alternator were smooth, but the crankshaft pulley jumped around like crazy. Just holding a pen near the outside edge of the pulley was jostling and jumping around, making me think the crankshaft itself wasn't rotating uniformly?

I took some photos and videos here, with the belt and alt-mount pulleys off to try and isolate the problem.

Aside from the dusting I'm not really sure there's a problem here, nor how I would fix it, so maybe I just live with the dusting. But curious if folks have any insights.

https://photos.app.goo.gl/sSSo6uZGvm6ydW8f6

Thanks!
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Old 19-02-2024, 11:19   #2
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Re: Pulley alignment; serpentine belt dust

With a properly running serpentine belt any "dusting" should be minimal in fact very close to none. What you describe I would consider serious wear. I mean, the dust IS the belt chewing itself up as it tries to adapt to misaligned pulleys. I have no way of knowing how long a belt will last under such conditions, but it will be greatly shorter than it should.

The videos do not give a clear indication of the problem to me. I would think it very unlikely to have measurable end play with a crankshaft, because if the crankshaft was moving axially, that would very quickly destroy the engine. A little runout is possible, but basically I do not think the sepentine belt pulley is parallel to the others. Not sure which one(s) need to be fixed...

You need to measure these alignments with the engine OFF, and rotating by hand. Not for safety reasons, but it's the only way to do it with any accuracy.
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Old 19-02-2024, 21:27   #3
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Re: Pulley alignment; serpentine belt dust

Thanks for the reply and advice. I will go back and triple check the later alignment.

Also,

- I added a few photos showing what I mean by dusting, it's particularly evident on the red alternator.

- There was some minor abrasive sharpness on two of the pulley faces where the belt runs, potentially contributing to the dusting. I sanded them smooth with 600 grit.

- I was finally able to PB blaster and remove the crankshaft pulley. There's nothing obviously wrong with the shaft itself, but I don't understand holding the radial dial gauge against the outside edge of the pulley (as seen in the 0:58 second video) has so much more movement than the other two pulleys. I'm going to take the crank pulley to a machinist to make sure it's uniform around.
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Old 20-02-2024, 18:21   #4
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Re: Pulley alignment; serpentine belt dust

I would offer three things, none of which may be applicable to your situation.
1, Do any of the pulleys have more grooves than the belt has ribs? If so, it's easy to have a belt shifted over a rib/groove either way.
2, Is the belt a best quality, like from Gates or Browning, or is it some imported product of unknown origin/quality?
3, X-amount of deflection with Y-pounds force tells nothing about tension without the factor of a specified distance of free/unsupported belt span.
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Old 20-02-2024, 20:09   #5
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Re: Pulley alignment; serpentine belt dust

Quote:
Originally Posted by mattman View Post
Thanks for the reply and advice. I will go back and triple check the later alignment.

Also,

- I added a few photos showing what I mean by dusting, it's particularly evident on the red alternator.

- There was some minor abrasive sharpness on two of the pulley faces where the belt runs, potentially contributing to the dusting. I sanded them smooth with 600 grit.

- I was finally able to PB blaster and remove the crankshaft pulley. There's nothing obviously wrong with the shaft itself, but I don't understand holding the radial dial gauge against the outside edge of the pulley (as seen in the 0:58 second video) has so much more movement than the other two pulleys. I'm going to take the crank pulley to a machinist to make sure it's uniform around.
Let me be perfectly clear, that’s not the way to use a dial indicator, no useful information can be gained and the risk of personal injury is high. Can you comment on the single shiny vee peak in the first photo on the pulley and what appears to be belt damage that lines up with that shiny bit? Crankshaft pulleys are notoriously rough finished cast steel or iron with the only machined surfaces being those that are necessary for function and fit. The crankshaft will typically have .002”- .005” end float, any less would cause problems including the crankshaft seizing and stopping the engine. If the belt dust is only what’s visible in the first picture, I actually wouldn’t be too concerned (unless that was only after 10 minutes of operation)
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Old 21-02-2024, 16:52   #6
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Re: Pulley alignment; serpentine belt dust

when using the Alt Mount on my Yanmar, I went through a few belts when I realized the pulleys were not in line. off about half a rib maybe. Also the paint and roughness on the crank was enough to make it not flat. Sanding and a light coat of paint fixed that.

I ended up getting a laser alignment tool to dial it in. Took a while of shimming and light grinding here and there to get them all all in line and all on the same plane. In my case, I needed to shim the alternator forward about the thickness of a washer.

Been great ever since. using the laser alignment tool made the errors show up quite easily.
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Old 21-02-2024, 18:40   #7
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Re: Pulley alignment; serpentine belt dust

Quote:
Originally Posted by phantomracer View Post
when using the Alt Mount on my Yanmar, I went through a few belts when I realized the pulleys were not in line. off about half a rib maybe. Also the paint and roughness on the crank was enough to make it not flat. Sanding and a light coat of paint fixed that.

I ended up getting a laser alignment tool to dial it in. Took a while of shimming and light grinding here and there to get them all all in line and all on the same plane. In my case, I needed to shim the alternator forward about the thickness of a washer.

Been great ever since. using the laser alignment tool made the errors show up quite easily.
Thanks! I've been debating getting one but they were all thousands of dollars. Can you share the details of the one you got?
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Old 22-02-2024, 07:06   #8
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Re: Pulley alignment; serpentine belt dust

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Originally Posted by mattman View Post
Thanks! I've been debating getting one but they were all thousands of dollars. Can you share the details of the one you got?
I got the Gates alignment tool.

not too expensive.

HOWEVER - the grooves on the tool are made for automotive pulleys, not the 10 groove on the balmar pulley. you can work with it, it just won't sit nicely in the grooves.

It is nice to put the laser on the pulley, then roll the pulley and see the laser go wonky if not aligned right. It really shows the minor error your eye couldn't see.

Installing the Balmar belt buddy made it easy to install, and dial in the tension
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