Hi guys, any help would be appreciated. Serial # 20062 4800 hours on machine The bucket cylinder on this machine wants to extend at all times (curl) with no movement of PPC valve. Removed lines from rod & head end of cylinder & tee’d in gauges. It has constant 100psi of pressure running to cylinder with machine running. Removed the PPC valve hoses that run to both sides of bucket section of main hydraulic control valve, no oil out of either hose & the cylinder still extending. I then removed caps, springs & spool which was snug.. NOT tight. Rolled it on a piece of 1/4” steel to make sure it wasn’t bent. Pulled the suction valves, checked the seats & the seals for the bucket section. Pressure/flow compensator was removed from this section too, nothing binding. Everything moves freely. I did obvious stuff first, cut filters open (clean) I did rebuild bucket cylinder first before starting to diagnosing. I pulled the main hydraulic control valve hoping to just replace the bucket section with Komatsu telling me that they do not just sell sections, the whole valve needs replaced. Once I got the valve to the shop, I split it & went through the safety suction valves, merge valve, unload valves, LS check valves. I will admit I messed up before pulling the valve I should have checked pressures to the other functions to see if it was a systematic problem. I’m at a loss, am I missing anything that I need to check? Thanks for any help guys.
I wanted to follow up with what I found just incase someone else ever runs into this in the future. This machine had a JRB quick attach on it which was removed but all the plumbing is still there but dead headed at the end of the stick. When diagnosing I just unplugged the connector to the solenoid valve to eliminate it, which made no difference & chalked it up as it was working correctly. Stuck the main hydraulic control valve back in, same problem, fired up & bucket curled instantly.. no surprise there. What I didn’t do was cap the lines that run the the quick attach which also use the bucket function. So that is what I did, sure enough it fixed the problem. The solenoid stem I’m guessing is stuck in the open position letting the oil make a loop & filling the rod end of the cylinder.