Hey, I just installed a hydraulic thumb on a JD 200C. The machine was plumbed already, so I connented the hyd. lines to the cylinder, but when I want to operate it with the toogle switch on right joystick, only the down move works. Cylinder won't retract. Any ideas what could be the reason? Maybe too much air in cylinder and lines? I am liitle low in hyd. fluid, will add some next time.
You sure it was plumbed for a double acting cylinder, not a hammer, rotator, etc.?
Have you checked for a directional valve in your hydro circuits?
No, I am not sure how it was plumbed. How and where can I check this? Also when I press the up button on switch, it sounds like pump is working, but the hyd. lines dont even move.
Follow the pipe from the right side all the way back the arm and boom, where does the hose go?
The line in question is the far right. Why are 2 lines feeding the one? There is some sort of turning valve just before the tee. What does it do?
One of those probably goes straight back to the tank, like for a motor. You are going to have to follow both lines off the thumb cylinder all the way back, and figure out how it is plumbed. That looks like it was setup to be convertible.
If it turns easy like a ball valve, it probably is a ball valve to let the return go right to the tank. Try turning that valve (edit: try turning that square stem) so the line is perpendicular to the flow, so turn it 90 degrees whichever direction it turns easy.
This is where the teed of line connects. Viewed from underneath.
Other line connects somewhere on top. Maybe tank, I dunno.
Close the ball valve as delmer said. That closes the path to tank and returns oil to control valve, then, when you tell the thumb to open the oil goes to the cylinder to open instead of straight to tank. Before you do any of that, STOP! Has anyone adjusted your aux pressure down to 2500 psi or less? This is important if you don't want to destroy your thumb cylinder and contaminate your hydraulic system with shrapnel. Do not allow your bucket and thumb to work against each other until you have the pressure and relief in that circuit reduced. Don't take that chance. This is more important than whether or not your thumb will open.
Thanks for info. I always assumed they would have a lower set pressure for attachment lines. Sticker on cylinder says max. 1800psi. Does it mean I have to install a pressure reducing valve in each attachment line? Does such a valve need a return to tank line?
Your aux function should have a 2 stage main relief in the valve. Additionally you should have port reliefs to unload circuit pressure when the bucket works against the thumb. If you haven't been down this road, its better to get an experienced hand in there. Too easy to get hurt or make a catastrophic mistake. MG2361 should be along shortly ,he can speak directly to the ins n outs of Deere. Obviously, since your cylinder is marked 1800, that becomes your top end pressure for the aux circuit.
Update: I measured the pressure in aux. lines, it read just over 2,000psi. Cylinder is rated at 1,800psi, I think I can leave it that way. I also turned that ball valve and now the thumb opens up, so that fixed that problem.
What are your port reliefs set at. If your bucket closes your thumb and the port reliefs are at 4k, you now have 4k in your cylinder. No good. It's your project, I would back out the safeties as well.
Fit a 5-port crossline relief valve (1800 psi) across the A and B lines to the thumb. 5th port does to tank for pressure relief, and make-up oil for anti-cavitation.