Hydraulic issue.... The Blade on my mitsubishi excavator started slowly bleeding off when pushed "down", lifting the machine... and it has gotten worse. Now its almost unusable as the blade has no down pressure at all except at full throttle, which still is not enough pressure to lift the end of the machine off the ground.. I thought it may have been a bad cylinder seal, so i rebuilt the blade cylinder which didnt help the problem, but seems to have made it worse.. The "up" pressure is good and doesnt bleed off when I tested it by pushing down on it with the bucket.. There are no external leaks and im wondeing where I should start looking for the problem.. the resistance of the spool valve for the blade has not changed and feels the same.. Im assuming it must be in the swivel section, but hopeing someone will offer a better, easier option to check first that may expose the issue.. Any other Suggestions as to where I should look before tearing into the swivel would be greatly appreciated.
Not real sure....and definitely not a mechanic on these things, but it is my understanding (on my Yanmar) that I have a separate gear type pump that controls my blade function. My blade is weak also, and I've just been figuring I'll have to replace that pump at some point. There may also be a pressure relief valve that could be dirty, sticking or faulty.
Resolved.. I removed the center swivel and found the polyurethane Oring seals to be faulty (worn out).. one that contained the "blade up function" was eroded away and crumbly.. I was going to replace them with oem urethane orings, but at $35 each, i decided against it.. I needed a total of 8 I replaced them with viton orings, much easier to find and which should work well, as most center swivles in larger machines use regular buna nitrile seals.. viton is more durable. To R&R the swivel, it was easy enough and the only issue was that the fittings were rusted so bad I needed to apply heat to remove them.. and its kinda heavy. It now works as it should..
Great work. Thanks for the update.