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#12 motor grader

Discussion in 'Motor Graders' started by Leonard J Rousseau, Oct 22, 2020.

  1. Leonard J Rousseau

    Leonard J Rousseau Member

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    My cat #12 Motor grader clutch is stuck engaged . i parked it on a hill in gear for two years and now the clutch wont let go.
    70D795 oil clutch. any ideas? thank you
     
  2. Vetech63

    Vetech63 Senior Member

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    I'm not positive on that model but it sounds like the friction disc is rusted to the flywheel or the pressure plate, or both. In most cases they will free up with a few lunges. Need a CAT guy to confirm any other option.
     
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  3. Leonard J Rousseau

    Leonard J Rousseau Member

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    with an oil clutch will they rust?
     
  4. ovrszd

    ovrszd Senior Member

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    It's my understanding that the "oil clutch" part is the engagement/disengagement method, like a hydraulic clutch system on a pickup or Jeep.

    It's possible that your "slave cylinder" that the pedal pushes has lost it's prime and is not disengaging the clutch. They can be bled just like bleeding hydraulic brakes. Look for a reservoir that would indicate oil level.

    It's also probable, as indicated by vetech63 that the clutch disc is rusted and stuck.
     
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  5. Leonard J Rousseau

    Leonard J Rousseau Member

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    Thanks for the reply, but there is no slave cylinder. the linkage goes directly from the pedal to the engagement/disengagement part of the clutch. i took the linkage off the pedal and put a comealong on it to eliminate any adjustment issue. In other forums people indicated that in an oil clutch the discs would not rust together. but I'm not sure that's true or maybe i just misunderstood. For the dry clutch people talk about dragging it in gear with the clutch depressed to break it free. I might give that a go. does anyone know, should i use a low gear or high gear?
     
  6. 56wrench

    56wrench Senior Member

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    i personally would try high gear first- less likely to damage anything and try it gently at first
     
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  7. Delmer

    Delmer Senior Member

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    If you're dragging it, use high gear. If you start it in gear, and drive it over a bumpy field, use lower gear.

    I suppose an oil clutch could stick if it got condensation and sat for years, that would still be unusual though. You should be able to see a dry clutch through some sort of access plate, you might see an oil clutch, but you'll get a face full of oil first. knowing which should help a little.
     
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  8. ovrszd

    ovrszd Senior Member

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    By your own description, it's not a hydraulic clutch. It's mechanical. Pushing the pedal will not break it loose. As suggested, use high gear if you are going to try towing it to break it loose.

    Several manufacturers recommend "blocking" the clutch pedal in the disengaged position if parking the machine for any length of time.
     
  9. Terry140

    Terry140 Member

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    Not sure if this is any help, but this is the diagram from the Cat 12 operators manual showing the clutch 20201024_100004.jpg
     
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  10. Tugger2

    Tugger2 Senior Member

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    I have a Cat 12 that i bought with a stuck clutch. I loaded it without clutch . Got it back to the shop and tried all kind of pushing with the pedal pushed down ,to no avail . we finally pulled the engine and had to wedge and pry the clutch disc of the flywheel. Hate to say it but thats your fix .
     
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  11. DB2

    DB2 Senior Member

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    I would try backing off the internal adjustment and make a few attempts at starting out in high gear. Trying to get the clutch to slip if you will.

    If that doesn’t work it’s probably disassembly as Tugger states.
     
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  12. Old Magnet

    Old Magnet Senior Member

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    Take the inspection cover off the left side and check to see if the clutch release collar is moving. Might be rusted to splined shaft. Are you getting pedal movement?
     
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  13. ovrszd

    ovrszd Senior Member

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    Good stuff Terry!!!! Thanks for posting the manual pic!!!!
     
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  14. Leonard J Rousseau

    Leonard J Rousseau Member

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  15. Leonard J Rousseau

    Leonard J Rousseau Member

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    Yes when I looked through the inspection cover the pedal is moving the mechanism inside.
     
  16. petepilot

    petepilot Senior Member

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    quart of kroil and a long spouted pump oil can` soak it down & let it sit couple days
     
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  17. skyking1

    skyking1 Senior Member

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    ^that is worth a try!
    I can see how it would ultimately rust up as the oil drained down.