stevblev
New member
Hey everyone. Going to try to make a long story short here. Pretty much my tractor was working fine until one day it decided to dump hydraulic fluid in the crankcase. I knew it blew a seal in the hydraulic pump but thought that maybe a valve somewhere was creating too much pressure on the pump causing it to fail. The 3pt would drop like a rock if I shut the tractor off. So far I have taken off the flow divider valve, relief valve, live pto valve, and the control valve, disassembled, cleaned and reassembled. I rebuilt my hydraulic pump and that has fixed the issue with the 3pt dropping, it holds strong now when the tractor is not running. Now on to the problem I am having.
When operating the 3pt, it will not hold position in between all the way up or all the way down, it jumps or hiccups violently like it has air in the lines. I have ran it probable over an hour operating the control lever so all air should have worked its way out by now. It does this with or without weight on the 3pt. I hooked a pressure gauge to it and with the 3pt all the way up it holds steady around 1700psi, which is roughly 200 lower than what my book says it should relieve at. In the middle position pressure fluctuates a few hundred psi. Im thinking that my control valve is either out of adjustment or has worn o rings.
My shop manual says to check adjustment, put a .400 shim in between the valve plate and valve body, which pulls both spools out .400. Then it says that if you put air in the unloader valve bore without the spring in it, and a .012 feeler gage between the double nut on the poppet valve and the valve plate, air should come out of a hole on the front of the valve. If you put a .024 feeler gage in the same spot, air should come out of a hole in the top of the valve. It does not describe how to adjust it if it is out of adjustment. The only thing I can change is the position of the double nuts on the poppet valve, but it has no effect on where the air comes out. The only way I can get air out of the hole in the top of the valve is to remove the .400 shim and push the spool valve in .060-.100. I feel like the air is maybe bypassing the o ring on the check valve or the poppet valve.
Does anyone have any ideas? Im not very experienced with hydraulics and hope I have explained this so it can be understood, thanks!
When operating the 3pt, it will not hold position in between all the way up or all the way down, it jumps or hiccups violently like it has air in the lines. I have ran it probable over an hour operating the control lever so all air should have worked its way out by now. It does this with or without weight on the 3pt. I hooked a pressure gauge to it and with the 3pt all the way up it holds steady around 1700psi, which is roughly 200 lower than what my book says it should relieve at. In the middle position pressure fluctuates a few hundred psi. Im thinking that my control valve is either out of adjustment or has worn o rings.
My shop manual says to check adjustment, put a .400 shim in between the valve plate and valve body, which pulls both spools out .400. Then it says that if you put air in the unloader valve bore without the spring in it, and a .012 feeler gage between the double nut on the poppet valve and the valve plate, air should come out of a hole on the front of the valve. If you put a .024 feeler gage in the same spot, air should come out of a hole in the top of the valve. It does not describe how to adjust it if it is out of adjustment. The only thing I can change is the position of the double nuts on the poppet valve, but it has no effect on where the air comes out. The only way I can get air out of the hole in the top of the valve is to remove the .400 shim and push the spool valve in .060-.100. I feel like the air is maybe bypassing the o ring on the check valve or the poppet valve.
Does anyone have any ideas? Im not very experienced with hydraulics and hope I have explained this so it can be understood, thanks!