PC400LC-7EO S# A87397
I will try to keep this brief but there is alot to this issue.
The pilot controls on this machine just blank out at intermittent times, sometimes twice a day, other times 12 times a day. The operator says this has been going on for over a year and that it has lately been getting worse. He also says it seems to fail more when the weather is hot, not so much in cooler weather.
The Komatsu dealer has been out twice that I know of at this point. They have replaced the pressure reducing valve, the pilot on/of solenoid assembly, and the screens in the output lines at the main pump. Now this was thrown n my lap about 2 weeks ago. None of the fore mentioned has been a fix for this issue.
I started 2 weeks ago trying to narrow down whether this was a electrical or hydraulic problem. No fault codes are present or stored. Each time this happens it lasts between 20 seconds and 3 minutes according to the operator.
1. The first thing I did is installed a 600PSI pressure gauge into the pilot supply line at the manifold under the floor that supplies the pilot pressure for the left, right, and travel valves. It is a steady 450 PSI when the safety lever is in the operating position and 0 PSI when in lock.
2. I also installed my multimeter on the electrical supply side of the micro-switch that operates the pilot on/off from the safety lever. I moved this to various locations as I got reports from the operator. Locations tested were supply voltage before the switch, after the switch, and at the solenoid valve itself.
After 2 weeks of various tests there never was a drop in the electrical voltage when the pilot controls would fail. In all locations the electrical stayed at system voltage when it was supposed to be there......which I believe is why there isn't any type of fault being detected electrically. I feel I have eliminated an electrical problem at this point.
On the hydraulic side of this is a different story. When the pilot controls blank out, the pressure has fallen to 0 PSI, 180 PSI, 250 PSI according to the operator. He is telling me it is all over the place. Keep in mind that this is so intermittent that I have yet to actually see this problem in person.......so I feel like I am chasing a ghost here. I did replaced the inlet screened banjo fitting in both manipulator housings and the travel valve just to eliminate any possible restriction. I also removed the pilot pressure manifold that feeds them just to make sure there wasn't part of a rubber hose or other contaminant inside causing any blockage.
Nothing on this is making any sense, and since the problem wont just fail and STAY failed, its been difficult to troubleshoot properly..........which leads to my next questions and any expert advise you PRO Komatsu guys may have.
1. The solenoid manifold on top of the main control valve is fed by pilot pressure. Can any of you give me a diagram of what each solenoid valve controls and its location on that manifold? My thought was the possibility of a leak in another circuit that could be dropping the pilot pressure.
2. Is there anything else in the merge valve that could stick/ hang up that could possibly dump the pilot pressure? I have NO hydraulic schematics on this machine to do any tracing myself. I'm just not sure where else to look in this pilot system itself and am wondering if my pilot pressure drop is somewhere other than where I am focusing.
Any help, advise, or past experiences would be beneficial at this point! I don't want to lose what is left of the hair I have and the dealer has given up.
I will try to keep this brief but there is alot to this issue.
The pilot controls on this machine just blank out at intermittent times, sometimes twice a day, other times 12 times a day. The operator says this has been going on for over a year and that it has lately been getting worse. He also says it seems to fail more when the weather is hot, not so much in cooler weather.
The Komatsu dealer has been out twice that I know of at this point. They have replaced the pressure reducing valve, the pilot on/of solenoid assembly, and the screens in the output lines at the main pump. Now this was thrown n my lap about 2 weeks ago. None of the fore mentioned has been a fix for this issue.
I started 2 weeks ago trying to narrow down whether this was a electrical or hydraulic problem. No fault codes are present or stored. Each time this happens it lasts between 20 seconds and 3 minutes according to the operator.
1. The first thing I did is installed a 600PSI pressure gauge into the pilot supply line at the manifold under the floor that supplies the pilot pressure for the left, right, and travel valves. It is a steady 450 PSI when the safety lever is in the operating position and 0 PSI when in lock.
2. I also installed my multimeter on the electrical supply side of the micro-switch that operates the pilot on/off from the safety lever. I moved this to various locations as I got reports from the operator. Locations tested were supply voltage before the switch, after the switch, and at the solenoid valve itself.
After 2 weeks of various tests there never was a drop in the electrical voltage when the pilot controls would fail. In all locations the electrical stayed at system voltage when it was supposed to be there......which I believe is why there isn't any type of fault being detected electrically. I feel I have eliminated an electrical problem at this point.
On the hydraulic side of this is a different story. When the pilot controls blank out, the pressure has fallen to 0 PSI, 180 PSI, 250 PSI according to the operator. He is telling me it is all over the place. Keep in mind that this is so intermittent that I have yet to actually see this problem in person.......so I feel like I am chasing a ghost here. I did replaced the inlet screened banjo fitting in both manipulator housings and the travel valve just to eliminate any possible restriction. I also removed the pilot pressure manifold that feeds them just to make sure there wasn't part of a rubber hose or other contaminant inside causing any blockage.
Nothing on this is making any sense, and since the problem wont just fail and STAY failed, its been difficult to troubleshoot properly..........which leads to my next questions and any expert advise you PRO Komatsu guys may have.
1. The solenoid manifold on top of the main control valve is fed by pilot pressure. Can any of you give me a diagram of what each solenoid valve controls and its location on that manifold? My thought was the possibility of a leak in another circuit that could be dropping the pilot pressure.
2. Is there anything else in the merge valve that could stick/ hang up that could possibly dump the pilot pressure? I have NO hydraulic schematics on this machine to do any tracing myself. I'm just not sure where else to look in this pilot system itself and am wondering if my pilot pressure drop is somewhere other than where I am focusing.
Any help, advise, or past experiences would be beneficial at this point! I don't want to lose what is left of the hair I have and the dealer has given up.
