Just purchased. 8k hrs. Seems to be well maintained but the problem I'm having is when traveling, it's dead slow. Same in lower, med and high speeds. Even under full RPMs and auto idle off...doesn't matter. What does work is when you stroke the pump by touching any of the main joystick controls, you can hear the pump kick up and we start moving as usual. That's good until it "calms down" again and then back to very slow. I have gauges on the way I've ordered. Any idea where to start and what to do?
Your machine is a closed center system. This means with the engine running and no hydraulics doing work, the pump is commanded to minimal displacement. Pressure rises to rated pressure (around 5100 psig typical) with excess flow passing by the relief valve and back to the tank. The reason you want minimal pump-displacement/flow in this condition is because all flow is excess, and passing full pressure through the relief introduces significant heat into the oil – thus it is desirable to have minimal flow with the machine at idle doing no work. When you go to use the machine however (command the pilot circuit to move a hydraulic load – e.g. boom cylinder, bucket cylinder, travel motor, etc) the LS valve detects the applied hydraulic load via pressure-drop on the main pump outlet, and commands (controls) the variable displacement pump feature to increase displacement. The purpose of the PC valve is to control the upper side of the pump curve. The PC valve will limit displacement so that the pump is not over-pressurized/overpowered during operation. Both valves work together. There’s a good functional description (quite in-depth) in the maintenance manual, but the troubleshooting guide is severely lacking IMHO. It sounds to me like there’s a problem in the LS/PC valve circuit in your main pump. A replacement LS valve is 150 bucks. The PC valve is a bit more. If it were my machine I’d start troubleshooting at the LS valve. It sounds like the pump is being erratically commanded to idle under light loads. The most likely cause IMHO is a faulty (sticky) LS valve, or possibly the PC valve is faulty.
Ok Noted. I did notice today that when I switch to Power mode and turn up the throttle all the way, that i didn't have any issues with demand for the machine to trek. Economy mode however, its what it's normally defaults to
These are both very good suggestions, considering the cost versus getting a tech out, especially with the hours on it. New machines are over $300000 now in Canada, few dollars to get back into shape is well worth it. Simon C
More to add to help paint the picture. I've only put 60hrs on the machine. The hydrualic fluid looks clean and full and the filter was allegedly replaced. I have a new one so I may replace for piece of mind. Cheap insurance. The machine seems fairly well taken care of. Around 8K hrs. Other than the problem crawling, all of the other functions work great. No drift, smoth and not jerky. No leaks. As soon as I move the boom, stick, or turn it revs up and works, then auto idle back down. Like I said, it's just not that simple when I was to walk forward or backwards, I have to stroke the pump. Should it do this in Economy? I feel like when I was in Power mode today that I didn't have this issue. Thanks for chiming in also. I'll also look into those items and figure out where to get them. Any recommendations on online parts stores would be great.
Komatsu filters are expensive, but quality is at a price. When you do change your filters, cut open the old ones to see what is in them as you might as well find out sooner than later if something else is going on. I have a Caterpillar filter cutter and am very happy with it, maybe you can borrow one from someone. Simon C
This link has free online parts catalog: https://777parts.org/a1/ Komatsu has the same catalog, but they xxx out portions of the part numbers (very frustrating). Once you positively identify the complete Komatsu part number, you can use it to search the web for vendors/prices. It has been my experience that the same Komatsu part can vary significantly in price - depending on who's selling it. So shop around. . . . .
That's done every single year on the annaul of my Piston engine airplane. You can tell a lot about an engine from the contents of a filter i would say. Don't wanna see babbitt in there
Hello everyone! Are there any Russian speakers on the forum? Thank you.
I suggest you disassemble them and inspect them thoroughly. There is a very high possibility that one or both valves are stuck. 16. LS shuttle valve (R.H. travel). 19. LS shuttle valve (L.H. travel).
Check Codes?
I will try to explore that. I'm still new to the machine, but it doesn't have any that pop up. I'll have to figure out how to find them
Access to the diagnostics. Komatsu Dash 8 Monitor Panel
Sounds like pressure switch or wiring for travel isn't working which will cause pumps not to ramp up or ls pressures are low. Sounds more like pressure switch under cabin. Main reliefs could also be low but if pumps aren't ramping and will ramp off other circuits I'd be checking the pressure switches. Comp valve seals could also be blown
How do I find pressure switch you're referring to or what page of the service manual it's on. Then how do I test? With a volt meter?
As stated they are under the cab, remove the panel and look directly up near the valve for the travel leavers. You can check it on the monitor inputs in the monitoring service menu and if no input to controller check the switch with a multimetre and check power and ground then do some swapnostics
I'm going to be checking wiring connections also. I noticed that sometimes the travel alarm will work, then sometimes it does not. Also, left joystick button is intermittent if when holding it down....unless I'm misunderstanding that function wrong. Maybe this and the pressure switch is all in the same connection? As stated before, sometimes the travel works as should but mostly it does not
I have confirmed that when the travel alarm starts working again, the travel funcions as should. When the travel alarm doesn't sound, then I have the issues. I can also hear the alarm cutting in and out like it's running out of batteries. Any idea if theres a certain connector or area to be looking at for this? The 2 issues are related and my gut tells me it's a wiring harness or connector. Where do I look? We're getting somewhere, Thank you guys!
Problem Solved. Under the cab remove the floor pans and there is a the pilot valve (I belive thats the term). The 2 travel levers connect to the manifold there. There are 2 pressure sensors. 1 black (20Y-06-21710) and 1 red (206-06-61130). I replaced both and things are working normal again. Very easy and simple fix.
Thanks for posting solution. Simon C
You're welcome. Nobody learns if the solution isn't posted. Thanks for all the imput from everyone. I did learn quite a bit.
Thanks Marcus. You were spot on! This indeed was the problem and was a very simple fix.