Supposed to be looking at a JD 310J monday for front bucket curl not working correctly. I stopped by today and it has little to no downward power and sometimes tries to drop when actuating the bucket up. I'm new to heavy equipment with a solid background in automotive repair. Just wondering what I should check or look out for when I go look at this thing. Thanks for any help. :notworthy:drinkup
90% probability the bucket cylinder piston seals are hooped, could also possibly be a port relief valve issue at the loader control valve, but not likely. Could be both?
Thanks, Ill be tearing into it monday. Kind of a new world for me aside from fixing stuff with dad on the farm. This thing does't have a ton of hours on it.
Alright, after looking at this thing, the bucket has no downward force, it will drop when the crontrol is shifted toward down, but by gravity only. It will also drop when the control is in the up position unless it is held all the way over, then it will work almost normally. I have blocked off the cylinder with it in the center of travel and lifted the arm and there is no drop when pressure is against it. Just wanting a second opinion before I pull the loader control out and start looking for issues.
Don't pull the valve. Which lines do you have blocked off on the cylinder? The cylinder could be acting as one way because the piston seals are leaking. Imagine this cylinder is a hydraulic jack, you put oil in the cylinder the rod goes out, you release oil the rod goes in. You want to block off the extend (top port on the rod end since this cylinder is upside down) and LEAVE the other one connected, that should keep it from dropping even with the control valve operated both ways. If it drops, then the piston seals are leaking.
I had both lines blocked off at the piston for the bucket curl. There was no movement in the piston with both lines blocked off. I may be wrong but with no movement in the rod with both lines blocked, wouldn't that rule out the cylinder?
NO, imagine taking the piston off entirely, the cylinder will not retract with the ports plugged. If you push the rod in, the cylinder will burst or fail somewhere. Look up "pressure intensification" You need to block one off and leave the other open or with the control valve open so that you pressure test one side at a time.
ok blocked off one line on the bucket cylinder at a time and still no drop from the bucket, meaning it cannot be forced down or up externally. This leaves me looking back at the control valve correct?
Does sound like a control valve issue. Odd, this machine looks like it's a straight gear pump open center system.
With the other line open or the valve open? "the bucket has no downward force, it will drop when the crontrol is shifted toward down, but by gravity only. It will also drop when the control is in the up position unless it is held all the way over, then it will work almost normally" The easiest explanation is the piston seals. But I'm an amateur, and valves aren't real clear to me... There's the control valve failure modes, the cylinder bypassing possibilities, and the *&^% backwards JD bucket tilt linkage that's more confusing than the hydraulics.
with the valve open
Never mind. something jammed in the relief valve?
got the relieve valve out, looks clean. That was my biggest guess was a relieve valve issue.
Did you pull the main relief or the port reliefs? There will be a port relief at each end of the bucket spool right next to it.
Just the main relief at the moment going to pull the bucket relief now.
After some deliberation at the shop I have installed a new spool valve assembly at request. I got it installed and still the same issue. Only I did notice it is much worse with ride control engaged. the bucket will mostly hold position until ride control is turned on, then will drop rapidly.