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D6C Fan Belts Twisting

Discussion in 'Dozers' started by Metalman 55, Jul 24, 2020.

  1. Metalman 55

    Metalman 55 Senior Member

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    On my 10K6516 D6C, is twisting fan belts, then eventually they break which is logical.

    Going back a few weeks ago we replaced the alternator, found that pully on it somewhat worn, so replaced the pulley for a new one. It seems to fit fine.

    Only a few hrs on the new set of belts after the alternator & alt pulley change & today it twisted another belt. Alignment seems ok.

    Changed them out again & am keeping a close eye on them again.

    Neither the crank our fan pulleys seem to be worn bad as the belts are still a ways up from riding on the bottom as they should be.

    We are starting to think that the crank & fan pullies are the culprits from limited wear maybe?

    Any ideas on what makes the belts twist like that?
     

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  2. Welder Dave

    Welder Dave Senior Member

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    Is an edge of a pulley warped and causing the twist or the pulleys out of alignment?
     
  3. Metalman 55

    Metalman 55 Senior Member

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    Not that we can see. TBH its really hard to get a clear line of site because of how the machine is configured.
     
  4. Delmer

    Delmer Senior Member

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    Use a brazing rod, or straight edge to be sure everything is in alignment. A harmonic ballancer can slip. Are the belts put on too tight? or forced on over the pulley instead of loosening the adjustment?

    was it twisting belts before the new alternator?
     
  5. Bls repair

    Bls repair Senior Member

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    Are they a matched set of belts?
     
  6. Tinkerer

    Tinkerer Senior Member

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    The belts should be riding up on the flanges just like the RH one in your photo.
    The only time I saw a belt twist, the pulleys were out of alignment. Get a hold of a fan bade and see if you can shake the pulley.
    Check the profile of the new belts for an exact match to the angle of the pulley flanges.
     
  7. Metalman 55

    Metalman 55 Senior Member

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    They were not forced over the pulley, rather loosened.

    Yes, the twisting problem surfaced after the alternator was replaced, but the alt is an exact replacement. I am beginning to suspect an alignment issue that we need to get to the bottom of. As mentioned earlier, it is hard to get a line of site to check alignment.

    Belts are a match set BLS.

    Fan blade is tight & does not wobble at all.
     
  8. epirbalex

    epirbalex Senior Member

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    I would put the old pulley back on till you can replace them all .
     
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  9. Old Magnet

    Old Magnet Senior Member

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    Belts should ride slightly above the pulley groove. Check v-groove for u-shape wear pattern.
    For some reason the D6C's seem especially sensitive to pulley wear.
     
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  10. DMiller

    DMiller Senior Member

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    Suspect the pulley on fan &/or crank have erosion wear causing the belt to try to climb out of the groove which is typical of older machines, could be the new Alt pulley is narrower or wider by a slight amount pulling to one side the belt noted and that starts that climbing sequence much as a car on a road rutted by a larger machine. Reinstalling the old alternator pulley may help in the short term, replacing or refacing the other two pulleys may become necessary.
     
  11. mitch504

    mitch504 Senior Member

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    I had a lot of trouble with mid '90s CH Macks doing that. I finally found that the A/C compressor mounts were flexing.
     
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  12. Nige

    Nige Senior Member

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    The snip below is an enlargement from the photo attached to your OP. To me it appears as though your fan pulley is worn. The belt ought not to sit below the top of the groove like it is in the photo. It would be interesting to see what the other belt looks like in the fan pulley groove when it is correctly orientated.

    You may well have an alignment problem but I'm of the opinion that the wear on the fan pulley is what's allowing the belts to twist. There's also apparently a chunk out of the back side of the pulley that while it won't affect the belts could easily cause bearing failure due to inbalance. That would probably cost you a new fan and a radiator core.

    Also have a look at the state of the tensioner spring while you're in there. Quite a few of them have been updated.

    upload_2020-7-25_20-24-47.png
     
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  13. crane operator

    crane operator Senior Member

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    My western star with a 12.7 detroit loves to throw its alt. belts. Pulleys are straight, but I know the pulley's are worn/ dished. It seems like it will go for a long time and not throw them, and the next set it will throw right away- no rhyme or reason.

    I didn't know anyone sold "matched" belt sets any more. I can ask, but it seems like all I get is two belts that may or may not be close to each other.

    With worn pulley's - would it make any difference if they were toothed belts or a smooth v-belt? Most of my experience is from the ag augers/ grain moving, and I always thought a smooth one would slip quicker, but be less likely to jump than a toothed. It seems like the teeth make it more likely to climb/ twist.
     
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  14. kshansen

    kshansen Senior Member

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    Can't speak for Western Star or for that matter be sure what Cat sells is a "matched set" but they do list one part number and call it a "set of two" 2P6140 for this particular application.

    Not a V belt but at the quarry we had a Sterling(AKA Ford) truck for a water truck it had the Mercedes/Detroit engine in it, for get the model, might have been a MBE900. Anyhow it had one of those Poly-Vee belts for the fan drive. Short time after we got it I noticed that one of the ribs was tron off.

    So I replaced it with new belt which is a bit of a pain as truck had pump running off the front of crank. Short time latter noticed same thing one rib gone at the front. Again replaced and inspected very close to see if anything could be hitting it or if there was any out of line between the pulleys.

    Hate to admit it but never found a cause and the fact that the truck never got more than a mile from the shop and unless there was some idiot running it never got over 25 mph just decided I had more important thing to worry about. Also problem never progressed just shed that one rib and it would go for a year without any more damage. Have to wonder if there was some flexing of frame or motor mounts as the cause.

    Truck did have problems breaking front fender brackets that I fixed by fabricating new ones and those held up for the last years I was there. I just don't think that truck was ever designed to be run in a off-road application. Not that our roads in the quarry were that bad but some operators just think they are stunt drivers for the Duke's of Hazard T.V. show!
     
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  15. mitch504

    mitch504 Senior Member

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    Some years back, Gates announced that they no longer sold matched sets, because modern manufacturing techniques resulted in All their belts being matched.


    Right after that, they offered an ocean-front condo in Az, cheap.
     
  16. dozr

    dozr Senior Member

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    have had lots of rubbers come out on harmor balancer till you pull pan under and look will cause all sort of problem or just quite pulling belt will also make run hot
     
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  17. Metalman 55

    Metalman 55 Senior Member

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    Ok......our mechanic pulled off the front belly pan this morning & here is a few shots of the crank pulley.

    Seems the belts ride a bit low in the groove & the report back was pulley grooves were somewhat -U shaped, so he is going to order a new bottom pulley. He says the bottom one is worn somewhat worse than the fan pulley. Plans to do the front crank seal when he is at it, as it will be in the open...……..

    The report back was the alignment was good for all 3 pulleys.
     

    Attached Files:

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  18. DMiller

    DMiller Senior Member

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    MM55 I would SERIOUSLY consider doing the fan pulley while its down, and YES I know is an expense not needed but is downtime all that affordable either?

    A lot of abrasive(Dirt) and good hard belts make lovely lapping tools.
     
  19. Metalman 55

    Metalman 55 Senior Member

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    We would but Tony our mechanic tells me that there are availability issues with getting the top fan pulley.

    He also said that the top pulley changeout is an easy fix compared to the bottom one, so one step at a time I guess.

    Anyone know where there may be availability of good used or new top pulley?
     
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  20. Nige

    Nige Senior Member

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    2P-3807 was discontinued by Cat.
    Best bet is probably Offroad Equipment - www.offroadeq.com/ - or a similar organization in your area.
     
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