Komatsu PC200 LC-5

[MachineHead437]

Hydraulic cylinder failure. At first it was stuck in the retracted position when I turned machine off it. The cylinder did a slow drift extending I waited a couple minutes and then fired the machine back up and the cylinder immediately snapped back into the retracted position. My brother did, I'm still not entirely sure what but now the cylinder is hydraulically locked kinda in the middle no fully retracted but not fully extended and does nothing. It's not making any noise. There is no pressure to the control (spool) valve at all. The joysticks are hydraulically operated. Any suggestions would be helpful

 

[John C.]

I sounds like the nut came loose on the end of the piston. You will have to remove the cylinder and dismantle it.

Has this cylinder been repaired before?

 

[MachineHead437]

I am not sure if it has been since we've owned it or not. It may very well have an issue also but as of right now our main issue is lack of pressure to the cylinder.
We disconnected the hose before the spool valve that would take the fluid up to the cylinder and moved the joystick and no fluid came out of the hose. somewhere between the pump, and the ppc shuttle valve its losing pressure because when the joystick is activated it should be putting out approx 340 lbs of pressure coming thru that line. To the spool valve. I spoke with someone who's convinced it's electrical. But I was trying to get some other insights and see if anyone else has experienced this

 

[John C.]

What you are describing is the pilot oil to shift the spool? There are no electrical controls for the pilots on that machine unless it is a Hyper GX? If so you have a machine that was never meant to be in this country. I've seen several of these machines but only seen one book and I don't have access to it anymore. I may have some notes somewhere if that is the type of machine that you have.

If you have hydraulic pilot controllers in the cab I have seen debris get stuck in the control pistons that are move when you move the joystick. Take the lever off the top of the pilot control valve and see if one of the pistons are stuck.

 

[MachineHead437]

Yes I do have the hydraulic pilots. I'm working with someone who's fairly knowledgable about machines but doesn't do it everyday and we've been working on this for days and I feel like we keep going in circles I scoured the manual and gave him all sorts of info but it goes back to that whole I'm a woman I don't know what I'm talking about. I feel the issue like you said is in that pilot control. There is a solenoid valve between the pump and the controls from what he's saying and he's convinced that's where the issue lies. I suggested, as well as someone else, that we just swap the boom and the bucket lines they operate off the same Pilot control. But separate ports. And that would help use to decide if it was indeed the pilot or something else. I will take the joystick off this morning and check it out. Thank you. Sorry for the long response. Just very frustrating.

 

[lantraxco]

You're in the right area and your idea of swapping function sets of pilot lines is excellent for troubleshooting. If you can either identify the joystick as the problem area or eliminate it, I think you'll know what to focus on for repair.