I am working on a Komatsu PC-290LC-11 with no hydraulic or travel functions . Machine has 11k hours. The machine was traveling forward, lost all travel/hydraulic functions and the pump started making a cavitation noise, checked hydraulic oil level, it was at the bottom of the sight glass, removed and replaced the 2 strainers/filters in the tank. Verified I have no restrictions in suction line at bottom of tank going to pump . removed and cleaned Self pressure reducing valve on main control valve, verified hydraulic lock out is working/releasing Verified Damper is good. Looking for some guidance of which particular pressures I need to check to diagnose which component is causing my issue. Thanks in advance for anyone’s help.
If I were you, I would verify that the pumps are even turning. It sounds as though you may have lost the drive on the back of the engine.
I have inspected the damper that couples the pumps to engine , it is in good condition. Thanks.
First, When you raise the safety lever, do any warnings appear and suddenly go away? If no cautions or errors display, please go to service mode. Observe PPC pressure to each function, using the joystick, exercise that function. Do you see the pressure rise and fall? If no, you need to look at the pilot safety solenoid again. It is the one right next to accumulator on the end. Just because it works, doesn't mean it's working. There's the pin in the coil, and there's a pin in the manilfold, make sure it is free as well.
How much pilot oil pressure do you have.
When I raise and lower the safety lever there are no faults or warning.. just the icon on the display indicating it is either on or off. I will observe the PPC pressure in service mode and remove the pilot safety solenoid , I have not checked pilot pressure yet I’ll be back to machine on Monday I’ll put a gauge on and see, Thanks for your help.
When observing PPC pressure for each function I do see pressures rising and dropping.. they go up to about 48psi max. I did verify the pilot safety solenoid is working either way.
48 psi, not 450-500? 48 is not sufficient to do anything. What about pump standby pressure, what have you got there?
Yes only 48psi I only have Monitor access reading for Pressure readings at the moment - komatsu pressure gauge adapter is broke have one coming will now be tomorrow before I can hook an actual gauge up . Thanks 01100 front pump pressure 455 psi 01101 rear pump pressure 455 psi
Unload / standby pressure at 455 seems about right for the pump pressure. U can pull the test port.plug out of the pump outputs and see if anything comes out from the pump main delivery lines when cranking but judging there 455 of unload pressure seems good. Point oil if you don't have a gauge use the monitor pilot functions for the leavers when you flick the safety lock up the pressure control circuit for leavers and stuff is available to check in dash. Should be 32-38 bar roughly. If you are worried about pump I'd pull the mag plugs out of the bottom and check for metal, one for either pump.
Thanks for the Reply Marcrus, Yes going by the shop manual the 455 psi is in spec, using the monitor watching PPC pressures for boom and travel functions I have 0psi until I pull safety level and operate a function .. then I only have the 40-48 psi but that also tells me my pilot solenoid valve is working .. Based on troubleshooting it looks like the self pressure reducing valve could cause this issue .. I have removed and disassembled, I don’t see any visible issues, but the relief valve on the SSRV is not serviceable if failed to my knowledge.. I’ll have a new gauge adapter today. I did remove ports plugs on pump have good flow for sure.
I'd cap the line out of the reducing valve and check with gauge in the valve as there's a small Allen key plug on it or near it that's M10*1.25 and cap the output line to the epc stack / Christmas tree and check if pressure rises, I've had things like attachment pedals bypass and cause the pilot to drop off heaps. In the reducing valve was the spool below the relief moving freely, the poppet and seating relief good and spring not broken in the relief itself or did you not stop it completely ? Was the other big plug with spool under it good too? I'd check mag plugs and pull the swash plate angle sensor out too as I have had these break off before as well.
Also was the coin filter in the valve clean ? Have had those block up before
I checked the coin filter it was free of debris, on the self pressure reducing valve you mention a M10x2.5 plug.. mine does not have one this size.. it does have one that is about M6-M8 size… could this be it? Rounded up the caps and plugs to close off lines, I will try blocking off the valve a checking pressure Everything inside the reducing valve looked good and moved freely.. the spring was not broke.. mag plugs and angle sensors checked out good. Thanks for your help
So should be on the side I think it's next to the ppc pressure sensor on the block, like cab side of spr valve. It looks like a small head on it and the Allen key but when pulled out it's a bigger thread, definitely M10*1.25 Interested to see what you come back with.
Update on my troubleshooting, I went ahead and ordered a new Self pressure reducing valve.. installed .. immediately had good pilot pressure and functions.. after about a minute or 2 the main pressure starts to drop.. pilot drops.. no functions and pump starts making a noise.. I can pull strainers and re-install (strainers are clean) and machine will work again and then repeat same problem.. I feel like I’m dealing with a negative pressure issue now or a blockage.. suction piping good, strainers good, everything on top of the tank is sealed good.. could a blocked or stopped up return line be causing this issue? Checking those now
Clean oil and oil at a safe operable level
When you say strainers, are you talking about the in tank return filters? Do you have a clean drum to pump or drain the hydraulic tank into?
I think he was talking about "SUCTION STRAINER". I think he can differentiate between return filter and suction strainer filter
Yes to my knowledge there is the one suction strainer/filter and on the return you have a filter and a strainer. I do have a drum and a waster oil tank.. I may end up up draining and cleaning tank again. Thanks.
I think you may have deduced the negative pressure correctly. To determine that, I suggest you try 2 ways: 1/- Open one safety valve on the top of the hydraulic tank so that air from the outside can flow into the tank. 2/- Use an air compressor to put compressed air into the tank. 3/- Check at the suction port of the main pump. I have encountered the same error as you, after many days of headache, I finally found out that there was a foreign object blocking the suction port of the main pump.
That's why I enquired about the suction strainer. I wasn't knocking on the guys skills, just asking an honest question.
A very rare cause! But in the spirit of testing all cases, I recommend you try swapping the main pump line of the machine as there may be something wrong with the main pump #2 (front pump).
Update on my repairs with this PC-290, first off I appreciate everyone’s help and input.After replacing the self pressure reducing Valve, Cleaning/draining the hydraulic tank a couple of times, changed the filters/strainers in the tank once again . The machine has been operating fine overall. Same machine has recently developed an issue where the engine stalls under heavy hydraulic load. After some troubleshooting I determined cylinder # 2 is not firing. Diagnosed as faulty injector. This should help.
I have one more Question for the Komatsu guys.. same machine PC290LC-11 while operating travel functions opposite directions (to turn) or run arm/stick function in to relief machine will randomly loose pilot pressure.. and sometimes stall. when I loose pilot pressure I can tap on the pressure reducing valve and I have functions again.. pressure reducing valve is new.. I’ve also removed , inspected and cleaned .. no issues found.. obviously being able to tap on the valve would make me think something is sticking, I am leaning towards a malfunction with the merge divider valve that that self pressure reducing valve bolts to.. anyone ran across a similar issue ? Fluids/ filters, pressures all seem ok otherwise. Thanks in advance .
I have had issues with merge divider in the past but only twice and on older machines, odd though, also if stalling under heavy load and continues to I'd check PC epc on pump if it continues but definitely sounds like merge divider a bit but also arm in hydraulic stall will stall the engine if the PC epc isn't working, not sure about counter rotation causing that though haven't personally tried when coming across the fault.
Thanks for your reply.. machine is back available for me today, I’m going to remove and inspect merge divider and I will test the PC -EPC thanks for your help.
Any success with that pilot disapearing? Looks a lot like the excavator I'm working on PC220LC-8