I'm going to put it back together with the original seal (since it doesn't look anything like your failed one) and try something else. Any suggestions?
Okay Sevan, Let's have another stab at it.
You fixed the leaks, filter change and you put new Hyd fluid in and still no go.
We need to establish to see if we have flow and then if that flow get to hyd lift piston. You can remove the banjo connection on the discharge and run start the tractor with an assistant taking a bucket to catch the oil coming out. with that you can measure flow but not the pressure. it is a good test but I don't recommend it because it does not reveal what the lift control spool valve is doing. I'd check the system on the discharge size of the spool valve. Your hyd system is open center configuration, just simply if your spool valve handle on the 3-point is all the way down, cause all the flow to go thru spool valve back to hyd reservoir in the diffy housing. As you raise the 3 point level part of the flow goes to lift system and the rest to the diffy. When the spool is at it's highest point then all the flow is directed to the piston till the arm is risen to its highest point and then all the flow is returned to diffy housing. Attempting to raise the 3 point higher and you cause the safety relief valve to release causing a chattering noise.
Look the pic below, This the inside look at you lift cyl head head. You see four holes,
1st from the right with the oring is hyd oil discharge coming from the spool valve.
2nd from the right is the rate of drop needle valve, providing some flow as well to lift move the piston.
3rd from the right is normal flow from the spool to raise the 3 point arm. The opening only allows flow toward piston only becuase it has a ball check valve.
4th hole is open to the diffy to allow for oil release when the lift is under shock loading. This hole is also served by a very stiff spring and a ball check.
What you see here is two check valves in the lift head. The first with the big ball is for normal flow to the piston and second is a safety relief. The key is to remember is " a completely closed rate of drop knob" can only keep the arm from dropping but you can still raise the arm if it is half way provided you have flow.
What I would do take the nut off as shown in picture, and start the engine with an assitant to catch the flow. I'd make sure the lift spool is in closed position. At this time you should have no flow coming out, as you raise the lift spool handle to raise the implemnt flow should start. if you do not have fllow then either your spool is bad or your pump not flowing. Rate of drop has no role whatsoever here.
By the way if the pump is operational and spool is bad and you get no flow coming from the piston head then all flow must be diverted to the diffy reservoir.
All of that said, likelihood of bad spool valve is minimal and I thinks we're closing in on bad pump or main pressure relief valve is stuck open before any flow to the spool valve as pictured below.
JC,
