Hey guys, I just bought a PC 50 at a great deal , only problem is the blade will not hold machine up, it just bleeds right back down, I thought cylinder is bleeding by so I had it rebuilt, put it back on ---same problem so I'm thinking valve must be bleeding by once preasure is put on blade, so my question is " how hard is it to take off blade valve and have it rebuilt?" any advise before I just tear into it? thanks, Mike
I has been my experience with most all Komatsu excavators that the relief cartridge usually can be replaced to solve the problem.
Have you tried reversing the hoses someplace to see how that affects it? do this first if possible Could be a port relief, find the blade valve and see if it has a cartridge screwed into both ends, one for each hose port. If so, swap them, try again. Possible you have a leaking seal in the rotary swivel that carries fluid from the top to the bottom for both tracks, the blade, and the motor drains.
OK if I can today I will get to valve , check for cartridge screwed into both ends and if so swap them and then I will report back with how it acts after that, thanks for your time and knowledge, I hope to get this done today, thanks, Mike
LOL, you got in there ahead of me while I was stargazing!
ok I got lucky and had a few minutes, I was able to take top cover off and that gave me just enough room to swap hoses, fired it up and same thing,put blade down and pick up machine and within few seconds it sits back down again, what is my next move? thanks, mike
I'm thinking this points to a bad seal in the swivel. Any way to put a ball valve in one of the lines coming from the valve? Lift it up, close the ball valve, see if it still drifts.
Yes, I will have to make a trip to town and grab some fittings but I should be able to do that tomorrow, I can connect down by the cylinder rather easily, it doesn't matter which line? Pick machine up and turn valve off correct? Thanks, Mike
You can do that but it will only test the cylinder (not a bad idea even though you had it rebuilt) In order to test the swivel you will have to put the ball valve in the line above the swivel, either at the valve or at the swivel. If it's all steel tubing that sucks. We're after the line to the butt end of the cylinder, I assume the cylinder pushes out to push the blade down?
Remember komatsu fittings are 30 degree metric.
Yes you are correct, the cylinder extends to push blade down, I am lacking one fitting to test cylinder, I should have that soon and will put valve at bottom of cylinder and test and get back with you. So far have not run into steel tubing, all flexable hose so far so that's good. I haven't figured out what the swivel is yet but it sounds like I am working my way there LOL, I will report back as soon as I can, I appreciate so much your time , thanks, Mike
Something like this:
Thanks , that does help, I did get the valve and correct fittings today and will attach to bottom of cylinder , lift up and turn valve off and see what happens and report back, thanks, Mike
OK I put the ball valve at the base of cylinder, lifted it up all the way and turned valve off and it held perfectly like it supposed too. We could not get all the guards off so as to able to mount ball valve up close to valve and try again, hopefully an easy out will get things moving, once we get to valve ( hopefully in a few minutes ) which port do you want me to try? This valve has two ports looking down in front ( towards the bucket ) and two smaller lines ; looking down that hook up on the bottom ( I am assuming those smaller ones go back to tank once a certain pressure is reached but that is a guess on my part ) thanks again, Mike
Not familiar with this particular machine so I can't say for sure. Pictures? Should be two lines that run to the center swivel if you can see that, one for up, one for down, not sure which it will be. You might be able to actuate the valve and figure out which line pressurizes when pushing the blade down.