I am new here so let me start by saying Hello. I recently purchased my first excavator, a Komatsu PC120-6. It is a 1995 with 5000 hours. I am having issues with hydraulic power after about 30-45 minutes of use. Once the machine gets up to operating temperature it loses quite a bit of speed and power. Most noticeably lifting the boom. All other functions seem to slow/weaken a bit as well, however none as much as the lift. I am assuming this is a main pump issue. I gave it brand new SAE 10w oil as well as a new filter... this did not help. I have priced a rebuild.... $6k is the best I have found. To be clear, it is definitely a hydraulic issue. The motor is not bogging down at all, the hydraulics just seem to be bypassing. This is not a daily use machine, it is our yard machine used for loading our trucks. Before I drop $6k on a new pump I am wondering if there is anything else I should be checking?? Would a thicker hydraulic oil help? Could I have a relief valve issue? Any help or input would be greatly appreciated, thank you in advance! Dante
Did you check the easy stuff, fuel strainers, fuel filter, air filter and fault codes?
Yes. Definitely not an engine problem. The engine is consistent and doesn't slow up at all. As far as fault codes, it hasn't thrown any. According to the display, all is well
Spend $6,000 on a "rebuilt" pump that you are shot gunning or pay someone $500 to flow test the unit
Understood. Before buying any pump I definitely planned on confirming via flow testing at a dealer (haven't found any local on site mechanics). I'm just wondering if there is anything else I could check before loading up and trailering the unit 1½ hours away.
Is the hydraulic temperature abnormal? What is the hottest section? Check the pressures off the pilot pump or reducing valve. I think this uses a snap fast diag port
Look around on the pump for broken paint on the adjusting screws before you haul the unit in. A flow test would be a good thing but the problem is that most dealers don't know how to accomplish it in a way that will tell that the unit is definitely good or bad. What we did in the past was look for metal in the suction strainer before we did anything else. There are a few different styles of pump, pump controllers and main control valves that can cause what you are describing. A photo of the pump and the main control valve might help us point you in a new direction. It also might be better to get a service call out from a dealer if you can't find a knowledgable independent wrench who can help you. I've been called in on several machines where the pumps were changed and the problems did not heal.
Do those pictures help at all? The machine is a pc120-6 serial#52278
Bump
What is all the extra plumbing for that is installed in the radiator compartment? The pump is an early iteration with the pilot pump mounted on the back. As I recall the LS relief cartridge should be in the lower left bottom corner of the main control valve as you are standing at the boom and looking back toward the engine. I seem to recall there being two cartridges there and I don't remember at this time which is the LS valve. At any rate that cartridge would set the upper limit of output pressure. The other thing you can do to check the pump that I recall is disconnect the solenoid wire harness on the pump. As I recall that made the pump go to full stroke. The system is load sensing and the pump tries to maintain 300 PSI pressure above the pressure that is making a function work. All this is kind of complicated and nearly impossible to explain over the internet. Let us know what you find.