Heavy Equipment Forums Heavy Equipment Community

Komatsu pc128us-2. hydraulic issues

Kyle J Beairsto ยท 2021-10-03 00:02

I have an pc128us-2 excavator down on the dixy fire my operator was running the machine then shut it down to grease the machin and clean out the air filter. When he restarted the machine he had no hydraulic functions so he started to trouble shot it and we have taken the main line coming from the pump to the main valve off and we do not have any hydraulic pressure what so ever im trying to figure out where to go from here is there a bypass in the pump are the couplers faulty ? am at a loss i have never seen a pump just fail like this they usually slow down or get weak any help would be appreciative

Replies17
  1. #1John C.2021-10-03 11:25

    The problem sound electrical. Can you take a photo of the monitor panel and post it?

  2. #2Kyle J Beairsto2021-10-03 11:28

    Mine doesn't have the monitor panel it was before the break off in serial number it has the old style thats right next to the seat

  3. #3John C.2021-10-03 12:34

    That's a gray market machine and unfortunately I have never had the opportunity to work on one of those. I have done inspections on them and seem to remember there is a hydraulic system shutoff lever of some sort on the left side operator console. I seem to recall the arm rest moves with the shutoff lever. It shuts off pilot pressure to the machine control handles in the cab. You mention no hydraulic pressure. Did you check it with gauge? I have never known of a pump coupler to fail on a Komatsu but that doesn't mean that it can't happen. Did you check the oil level in the damper case? Is the paint on the housing between the engine and the pump discolored? Have you checked all the fuses with a test light or and ohm meter? This is an older machine so how many hours do you have on it? Send me a PM with a serial number.

  4. #4Kyle J Beairsto2021-10-03 12:40

    Serial number is 7124

  5. #5Kyle J Beairsto2021-10-03 12:43

    Didn't have a test Gauge had them brake main pressure line loose and start the machine and it had nothing

  6. #6Kyle J Beairsto2021-10-03 12:45

    So that's one of my questions will the pump just recirculat in it self if the safety switch is on

  7. #7Kyle J Beairsto2021-10-03 12:46

    Damper case?

  8. #8Kyle J Beairsto2021-10-03 12:46

    No discoloration on the pump housing and we checked all the fuses

  9. #9Kyle J Beairsto2021-10-03 12:47

    7000 hours

  10. #10Kyle J Beairsto2021-10-04 13:34

    So I pulled the plug at the end of the pump where and had my guy start the machine and the shift inside did not turn

  11. #11John C.2021-10-04 20:44

    Then either the pump is broken on the inside or the damper and pump input shaft is ruined. The pump has to come out either way. It only takes two to three hours tops to pull the pump itself. The counterweight though might be a little more problematic.

  12. #12Kyle J Beairsto2021-10-04 20:49

    May I ask what the damper is? Also I've had the counter weight off several times in the past so I have to tools to make it happen I will keep this updated

  13. #13John C.2021-10-04 21:00

    The damper is a flex plate that looks like a clutch plate with no friction facings. It bolts directly to the flywheel. In the center there is a female splined coupler that the pump input shaft engages into. You can only access it by removing the pump from the back of the engine.

  14. #14Kyle J Beairsto2021-10-11 14:19

    so the coupler that bearing went out causing the shaft to bind then it spun the the coupler shaft teeth

  15. #15John C.2021-10-11 18:51

    You will have to remove the pump to see what exactly happened.

  16. #16Kyle J Beairsto2021-10-11 19:01

    I already have thats what had happened the bearing went out I ordered parts put it back together and it's back up and running

  17. #17John C.2021-10-11 19:03

    That is super. Glad to hear you got it fixed!