Hello HEF! First post here but I have been reading for a while. I picked up a 1989 PC200-LC3 about a year ago. It was originally setup with a denharco d3000 stroke delimber (still functional). I found a used boom assembly locally and last week swapped it on the machine. The issue I am trying to figure out is that the arm won't hold. I have basic knowledge of hydraulics but I need help figuring out if the issue is related to the spool or maybe an adjustment that I'm missing. The arm citrcuit is constantly running fluid. It sounds like a leaky toilet tank. The machine has joystick control and all is normal at the stick. I remember the guy I bought it from mentioning the delimber grapple being designed to keep a bit of pressure which it did, the claws would slowly close all the time. Could it be that the spool assembly is just worn out, or is there a spool designed to bypass like this and it needs adjusted?
Good day Do you have the hydraulic schematic for the original setup, maybe we can see what is going wrong from that information. Kind regards Uffex
Good morning, I have a digital copy of the shop manual but it's on the computer at the house. The machine is on my homestead out of town on the mountain. It was built out of Canada as a logging machine so there are customizations that aren't in the books. All the power is there and it digs, the arm just has no hold pressure and bleeds off. My excavator buddy said he had a similar situation with a jcb excavator where something let loose in the system some junk scratched a spool. He also said it's possible for the arm cylinder to be leaking internally. If that was the case, it wouldn't explain why the grapple on the delimber was leaking down as well, so it's got to be in the machine. The hoses from the joystick plungers go right to the spool caps on this circuit. The hoses from the circuit run to a 6-port distribution block above the swing motor. Attached pics of the control valve. The circuit is on the right second one up from the bottom. Has the overload valve on it. I tried switching the overload for a plug and there was no change in the issue. Are the spools 3-6 the same? I have the parts book with me and they look the same but have different part numbers. I was thinking about swapping them and see if the issue follows the spool. I just want to make sure from the people that know more than me about it that I'm on the right track before I drain the control valve and get into it.
Pic of the distribution block. Aside from the six distribution ports, there's two additional connections on this block. One on each end. I believe they are returns for the aux control, but could that have something to do with what's going on? We capped the one going back to the tank when we pulled the delimber, but there is still a hose hooked into the end on the other side of the block.
Good day The only logical suggestion I can make is to make a good note of the standard arm hydraulics from your manual and work from end to end. You will need to post a copy for help as I do not have -3 information. Kind regards Uffex
Thank you for the replies. I will get a schematic uploaded this week.
Based on the attached info there is a throttle valve with a special spool for arm in under no load. The purpose is to prevent more oil leaving the cylinder than can be supplied. This is what is happening, under no load if I let the arm drift down on it's own then pull the joystick to arm in, the arm hangs there and it takes 3-5 seconds to supply enough oil to bring the arm in from center.
Is the arm creeping in, out, or both directions?
And is the cylinder underslung or overslung?
It falls back to center of gravity from both directions. I have to keep slight pressure on arm out to keep it from moving. Cylinder is overslung.
Have you tested the cylinder?
I have not. Same issue was going on previously with the delimber attachment on that circuit which has two cylinders for the grapple. That's not to say there isn't an arm cylinder issue, but the commonality is the hydraulics on the machine.
Is the stick circuit plumbed the way its shown in the schematic?
It is plumbed as per the diagram yes. When I was hooking all the lines up for the first time, I mixed up the arm with the aux circuit which activates by the toggle on top of the joystick. I corrected that, but come to think of it, the arm didn't drift when it was on the aux circuit... as of now, I can hear the fluid bypassing somewhere internal, I just can pin down where with all the motor noise
if its plumbed as shown in the schematic, the only things that would cause the stick to creep in are the cylinder, stick in circuit relief and arm low spool. The check valve that separates arm low and arm high could be leaking too, but the arm high spool would beed to be leaking as well, so it could be the problem but its unlikely. If its creeping both directions, its either the cylinder or the spool, or you have 2 different problems, like 2 leaking circuit reliefs. I agree that if the problem was there before the stick went on then its probably not the cylinder, but it takes 1/2 hour to test so its an easy one. Id go after the reliefs second since theyre pretty easy to get at as well. Maybe someone backed them both off at one time?
That sounds like its eliminated the cylinder then