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Cat 740b brake issue

Discussion in 'Other Earthmoving Equipment' started by Jdgreen420, Feb 1, 2018.

  1. Jdgreen420

    Jdgreen420 New Member

    Joined:
    Feb 1, 2018
    Messages:
    1
    Location:
    New york
    Hi, I have a Cat 740b haul truck. I have just recently performed a 1000 hour service on the machine. All new filters and fluids. My operators are now complaining that the brakes will not hold them loaded on slopes and the brakes require much more effort then it had previously. After changing the hydraulic fluid it took a while for both the hoist/brake system and steering system to stop cavitating but after about 30 seconds everything seemed normal. After the complaint I bled the brake system at each wheel thinking their may be some air in the system but that did not seem to help the issue any. If you're hard on the pedal the machine will over power the brakes around 1500 rpm. Will hold the machine on the slopes fine empty but not loaded which It had no problem doing before. Any suggestions would be greatly appreciated!
     
  2. kshansen

    kshansen Senior Member

    Joined:
    Mar 11, 2012
    Messages:
    5,332
    Occupation:
    Retired Mechanic in Stone Quarry
    Location:
    Central New York, USA
    Not being there or having worked on one of those trucks, at least not that model, Two things I can think of is checking brake pump pressure and checking brake adjustments. See file below
     

    Attached Files:

  3. RjMaan

    RjMaan Active Member

    Joined:
    Mar 23, 2018
    Messages:
    25
    Location:
    Pakistan
    I think its the fluid that you have changed. If the fluid you used was same as used in previous maintenance then there would be some other issue but if the fluid has been changed by mechanic than it would be fluid issue because it is not providing enough pressure to stop the vehicle.
     
  4. Nige

    Nige Senior Member

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    Jun 22, 2011
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    8,922
    Location:
    G..G..G..Granville...........!!
    Fluid doesn't create pressure........ hydraulic system components create pressure.
     
  5. Nige

    Nige Senior Member

    Joined:
    Jun 22, 2011
    Messages:
    8,922
    Location:
    G..G..G..Granville...........!!
    If you say that you heard cavitating up to 30 seconds after starting the engine for the first time after servicing I would think it's likely you have air in there somewhere.
    See if this procedure helps.
    Also, have you tested that all the accumulators (service & parking) have the correct precharge pressure..?
     

    Attached Files: