Hello everyone thanks for having me, new to the forum here. So I have a komatsu pc45 I've been reviving. The boom down circuit is bypassing or not holding pressure and is weak. I've repacked the cylinder twice as I have done a dozen or so different ones over the years, recieved wrong orings the first time. I have visually inspected the spool valve and poppets. So I switched the hoses on the cylinder and the issue reverses. I switched the pilot lines and the issue also reverses there. So I am assuming it is the spool or poppet valve. I am pulling my hair out on this thing any advise would be greatly appreciated, thank you!
You say you are reviving. Was it working like that since you got it or started recently? Since the problem switches when you switch hoses, you probably are looking at a relief in that valve or something similar. Are the parts available for that spool and how hard to get at. Simon C
Hello yes been like that since I've had it. I bought it as is and been going thru cylinders and hoses and such and I am just now getting where I can test it. I can get to three sides of the spool, outlet and each pilot side. Haven't tried part searching, not sure what I need as visually everything looks good but obviously something isn't. I guess I can call the local dealer monday and see what they can get.
Depends how old it is but on some of the older stuff, the only thing you might be able to get is a circuit check valve or whatever Komatsu is calling it. Before you pull anything apart, make sure to wash around and blow heavily with high pressure air to make sure no spec of hard dirt falls in. Would need to have some quality caps for lines disconnected to keep things clean. Simon C