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Travel MotorProblem

Discussion in 'Excavators' started by AmericanLandMgt, May 1, 2011.

  1. AmericanLandMgt

    AmericanLandMgt Well-Known Member

    Dec 4, 2009
    Wilmington NC
    My Komatsu PC-120 has started doing something kind of funny. I have a feeling I am in for some pricey repairs but maybe you guys can tell me whats going on.

    When I am going to move forward or backward I push both levers all the way but the machine tends to pull one way or the other. Also, when turning I can hit the right hand lever and almost nothing happens,but if I just move the left hand lever a little bit the right lever responds pretty good.

    If I try to push the levers in opposite directions its very very slow. But if I just use one at a time I can walk it around pretty good.

    Also the left hand lever is getting harder to push and pull. It feels like a pivot point is really rusrty or something but I cant see anything that would be making it sticky.

    Are my travel motors going bad or is it something I can fix pretty easy?


  2. jey_c

    jey_c Senior Member

    Oct 21, 2010
    What is the dash number of your PC120?
  3. Chris5500

    Chris5500 Well-Known Member

    Oct 23, 2009
    Plant Mechanic
    Well, making an assumption based on what you have described above, I would be leaning towards a bypassing rotary joint. But like always, before replacing a component make sure you have diagnosed it properly and that it is actually cactus.

    To me knowledge there's been a fair few threads on these very forums with similar or identical symptoms as yours, if you do a quick search I'm sure you'll find a wealth of information on how to go about diagnosing what is wrong with your machine.

    Obviously thing's like pilot pressure, relief pressure, travel brake release pressure, travel motor case drain volume and quality etc are some things to be mindful of as well.
  4. YellowIorn

    YellowIorn Member

    Mar 26, 2010
    Equipment Operator
    My favorite old Samsung did something simaler, I'd say drain both final drives, if the one you suspect has an issue, you will probably fight the need to puke when the oil hits the drain pan if it is on its last leg. We changed fluid every50 hour and went close to 2000 hours before we had no choice but to fix it right.
  5. vcinri

    vcinri Member

    Aug 28, 2010
    Not to familiar with a Komatsu excavator, but I imagine it must have a center swivel. Check that the seals are not blown causing a loss of pressure. If the lever is getting harder to move, possibly a mechanical issue. I had linkage rust up on me in a Dozer that had pretty much the same symptoms as you described.
  6. John C.

    John C. Senior Member

    Jun 12, 2007
    Machinery & Equipment Appraiser
    Early machines of that size used a cable control system on the pedals. They tended to freeze up as they aged.

    The other issue is the straight travel system. There are a couple of switches that work off the pedals that are accesses under the cab. When the switches are closes they shift a valve on the right side control valve that joins the flow of both pumps. When one of those switches gets stuck it makes a mess of your operating and tends to overheat the hydraulics.

    Just some suggestions.