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PC 6-6 Again. Machine stops suddenly when rotating.

Discussion in 'Excavators' started by big builder, Jun 29, 2020.

  1. big builder

    big builder Well-Known Member

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    Hello Everyone,

    Well I was able to get the planetary seal done and the swing motor seal as well. Installed and working. Did a hydraulic fluid change with filters and stainers , greased up the swing gear, swing bearing and the entire machine. Was working on tracing some small hydraulic leaks but I have another propblem. It is stopping suddenign when rotating. I have be digging and swinging very slowly while I make sure my handiwork is ok. Things I know about this issue.

    - It started before I replaced the seals on swing planetary and swing motor but not long before.
    - It happens in either direction.
    - It will not push through it with the joystick. You need to let off on the joystick then it will keep rotating.
    - Seems to be happening every 1/4 to 1/8 of a turn now. Before it was every one or two turns.
    - Everything else seems to be functioning well.
    - I didnt see anything amis while I was greasing the swing gear through the access hole. Although it was very messy in there with a mix of grease, oil and water. I cleaned it out as best I could and put in 4 litres of lithium grease as specified and was going to add the balancde after running for a few hours.


    I really need to get this machine back up and running so any help diagnosing this would be greatly appreciated.
    -
     
  2. Bls repair

    Bls repair Senior Member

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    Swing break intermittently coming on . Something jamming up swing motor or gear box
     
  3. big builder

    big builder Well-Known Member

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    Hi, Thank you very much for the reply.

    I am not sure what that could be? I had it all apart recently and the gear on the planetary was in nice shape.

    I did a little puttering tonight and a few other things I know:

    - Idle speed does not affect it.
    - I bled the swing motor and it was fine.
    - Now it seems to be on a specific pattern. 4 to 4.5 time per 1/4 turn. In either direction. About 16 to 18 times per 360 degrees either direction.
    - The swing brake switch is functioning.
     
  4. Bls repair

    Bls repair Senior Member

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    I would have someone spin machine while counting how many revolutions the pinion gear makes between jam ups . This will tell you if it is consistent or arbitrary
     
  5. big builder

    big builder Well-Known Member

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    I believe its pretty consistant now. It wasnt before. Now it seems to be about 4 times per 1/4 revolution. I just redid the seal in the planetary and the gear looked good. Unless this problem could be inside the planetary? It has the bolt on gear so I didnt have to take it apart.
     
  6. treemuncher

    treemuncher Well-Known Member

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    There is a bank of pressure sensors where the low pressure pilot lines attach between the radiator and air cleaner. I had one of those go bad once. I don't remember the exact symptoms as to whether it was constant or intermittent failure. You can swap these sensors about and see if that changes the function that is affected.

    I do remember, at the time, the sensors were $125 each from Komatsu. I was able to purchase a qty of 5 from China, in original Komatsu packaging, for the same money including shipping. It was likely from Aliexpress.com . Because the 6 series is now older, parts are readily available at much cheaper prices from China rather than dealing with my local Komatsu dealer.
     
  7. big builder

    big builder Well-Known Member

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    Hi Treemuncher. Thank you very much. Are the pressure sensors related to the swing brake? I am not sure but I guess it must be either the swing brake, ring and pinion or the planetary swing gear that is the problem. Again I am not sure. These repair areas are new to me.
     
  8. big builder

    big builder Well-Known Member

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    I wanted to mention that is a pc -60-6. I miss spelled the title and dont know how to fix it.
     
  9. John C.

    John C. Senior Member

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    You need to plumb a gauge into the swing brake line and see if pressure to release the brake is constant. If it is, you might have to pull the swing motor back out and check that you put it back together right. I would hope that the problem isn't in the gear reducer but you never know for sure until you find the problem somewhere else. Good Luck
     
  10. big builder

    big builder Well-Known Member

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    Hi John, Thank you very much for the reply. As for the swing motor I didnt take it apart when I had it out. I just replaced the seal on the spline . Which is held in place with a snap ring only. And can only be install one way . Now I just got back from the shop. I was lookiing at the routing of the swing brake electrical and hydraulics. Took off electrical connectors to inspect. Looked ok. Then while sitting in the machine I applied the swing brake manually and observed the machines behaviour and the behaviour of the hydraulic lines ( two smaller ones) going into the swing drive motor. Oddly the machine worked fine for about 20 minutes and no stopping. Then its started doing it again. Fairly consistantly. But this time I watched the too small lines from the side window of the machine. Thats right they tense up when the machine stops. When I center the joystick the line slackens and the machine swings again over and over. So I am thinking that must be the swing brake applying itself? if that is the case what are the possible causes of that?
     
  11. John C.

    John C. Senior Member

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    I can recall why there were two small lines on the swing motor. It only needs one line to release the swing brake. I would probably make sure the two hydraulic lines didn't get accidentally crossed somehow first. If they are correct, I would plumb a gauge into the swing brake release line to machine sure the pressure was constant when released. It is possible the swing brake solenoid coil is going bad and not holding when it gets warm. The coil can be replaced instead of having to replace the whole valve if it is a problem. You can also swap different coils in its place that are in the stack together.
     
  12. big builder

    big builder Well-Known Member

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    Ok thank you John. I am working on trying to get a few parts for this. Its very frustrating. Not sure if I pursue the swing brake idea or whether I pull the planetary again and open it up and see if anything looks amiss in there. If it were yours what would you do?
     
  13. treemuncher

    treemuncher Well-Known Member

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    It's been a few years and some water under the bridge since I fixed my issue with my PC200LC-6 swing issues. I do remember that there is a swing brake release switch at the fuse panel that allowed me to continue operations until I fixed my sensor.

    My issue was a bad pressure sensor that caused my swing brake to come on. If I remember correctly, it was only in one direction that the brake would not release because there are 2 sensors on each pilot line - one for each direction of operation of a circuit. By swapping the pressure sensors on the swing pilot circuit, I was able to change the direction of the problem and prove that my issue was indeed the pressure sensor.

    By flipping the "brake release override switch" to the on position, I was able to continue operations until I purchased and installed a new pressure sensor. If you have this switch and it solves the problem, then you can be fairly certain the problem is in the swing brake circuit.

    Putting a gauge on the brake circuit is the best way to verify whether or not the swing brake is the problem and when it is being applied. If the brake is not being applied when the problem occurs, then it is time to look into the gear box.
     
  14. big builder

    big builder Well-Known Member

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    I will definately be looking into that. Thank you very much!
     
  15. big builder

    big builder Well-Known Member

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    Going over the manuals and this is shown in owners manual. But the diagram of where it is is ridiculus.
     

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  16. big builder

    big builder Well-Known Member

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    Found this in the parts manual. If I turn the swing brake off how does that affect operation of the machine? Can I still spin and run machine and dig etc. How will it affect the rotation?
     

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  17. treemuncher

    treemuncher Well-Known Member

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    Your owners manual pics won't load for me.
    If your cab is the same as mine, and it likely is on a PC60, on the right side below the display panel is the fuse block. There are two override switches on the bottom of that opening behind the cover. I think the swing switch is the one towards the rear.
     
  18. treemuncher

    treemuncher Well-Known Member

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    If I remember correctly, the machine will function the same as normal but the parking brake won't be applied when sitting still. Normally, the machine sets the swing parking brake within a few seconds once the swing function is centered. You might experience some swing drift if working on a slope.
     
  19. John C.

    John C. Senior Member

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    Komatsu calls the switch a prolix switch in most of their manuals. It bypasses the computer control of the swing brake and puts a constant voltage to the solenoid to release the brake. It doesn't affect any other controls at all. I have had several machines with the switch in bypass mode all the time. It will give you a 14 code on the pump control computer. Shifting the switch is a good way to tell if there is a wiring or solenoid issue. Then again if the solenoid or wiring is bad, you will get the code anyway.
     
  20. big builder

    big builder Well-Known Member

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    Gentlemen, Let me first say thank you again. Your knowledge is impressive. So I went to the shop and lo and behold I found a little red switch under the storage traybehind the seat. Just sitting there. I can watch the two hoses that attach to the swing motor for the swing lock function. I zip tied a few other hoses out of the way. As I watched I can see that the hoses twitch and a faint click of a solenoid when I apply the swing lock switch on the console. Likewise when I release it. I can also see the hose twitch when the machine idles for about 5 seconds. Releases as soon as I touch the joystick. Flicking the swing lock override switch stops the machine from automatically locking but does not stop the swing lock coming on if I turn the dash switch on. I dug for about 20 minutes before it locked up on me ( frustratingly intermittant). I held it locked with the joystick and flicked the swing lock override switch at the same time and it released and started moving again. It seems like it is a swing lock problem. But if I can keep the override switch on for now I will and get a project done to where I have time to work on it without a deadline.
     
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