I have a 2011 komatsu pc138-uslc8 and the hydraulics get jumpy almost like it has air in the system. It’ll only really do it when you’re working the arm and boom at the same time though. So far, i’ve done the procedure to bleed the air out of the system multiple times, step by step. I’ve changed the hydraulic filter, the ppc accumulator, and checked all the codes, nothing there. I haven’t pulled the suction strainer yet, but will monday and hopefully that may help. Anything else that i could possibly check or suggestions on figuring out the issue? I have the shop manual but haven’t had alot of luck with locating a troubleshooting of this. Thanks in advance
Have you checked for codes in the diagnostics section in the monitor panel? Have you done any cycle times on the boom up function? Does the machine walk a straight line? How many hours are showing on the hour meter?
Yessir, no codes there. Haven’t done cycle times yet, but i’ll do it first thing tomorrow. Also gonna try to monitor pressures and everything tomorrow. As far as i can tell it walks pretty straight, haven’t noticed anything irregular there. Currently showing 4229 hours
Did that event come on all of a sudden? Have you checked fuel and air filters? I don't know if you machine has the hidden fuel suction strainer? Do you have a Komatsu engine SD95 or a Cummins engine, I think SD104? What you are describing doing with the two functions pulls the most horsepower out of the engine. High flow with high pressure. Check your engine RPM went it happens.
It’s always been somewhat random. I bought the machine with 4k hrs on it and the batteries were bad on it, changed only to realize the alternator was also bad. So i was getting low voltage and chalked the issue up to low voltage possibly. After changing alternator and a bit later the belt, voltage was finally right and still had the issue. It would get jumpy multiple times a day, but not consistently. Changed both pre fuel filter and primary fuel filter, haven’t changed air filter. It’s the komatsu sd95 engine. With that being said, i haven’t noticed any lugging of the engine while performing these functions. I had just learned about the functions of the monitor diagnostics yesterday and went pulled codes, so tomorrow when i run i’ll monitor rpms and everything
So engine rpms drops like 200 rpms round about from what i can tell. What i did notice though was pump pressure drops from around 2800 down to around 500psi when this event happens. Engine torque ratio goes from around 50% to 100% and drops to 10% back to 100 and back and forth.
I'm thinking you might take a sample of the hydraulic oil and get it analyzed. Have you checked the oil level in the damper case? Something like that might happen if that was overfull. When working the boom and the stick at that same time are you raising the boom and running the stick out or in? Does it hunt when lowering the boom and bringing the stick in or out? It kind of sounds like something in the pump might be haywire but you need more info before pulling the pump for teardown and inspection. I'm guessing you don't know if the hydraulic oil was ever replaced.
So i checked the damper case, it was definitely overfull. I honestly didn’t know how to check it until looking it up, and i had never added any since owning this machine. Level is correct now, ran for about an hour and it started to act up again but not nearly as severe. Now it’s changed though, it’s only about half way in just using the stick, and halfway going out also. I’ve had to change one of the hoses on that ram twice before and it was the feed line. First time was from a hose rubbing, second time was a bad hose fitting. I’m kind of wondering if maybe the flat face fitting isn’t sealing off all that great and possibly catching some air? I could be way off in my thoughts on this but beings it’s only half way when it gets jumpy, and that’s the only time now is why i’m asking.
Air will not affect those functions. Was the oil burned and stinky? It will have had to come from somewhere. Either the rear main in the engine is leaking or the input shaft seal in the pump is leaking. I would suggest you check the level again.
Yea it was definitely dark black, and somewhat had a smell. I’ll check here in a second. Definitely gonna let it cool down again, and check engine and hydraulic levels again just to see if i can tell where it may be coming from