SOS, I have my first tractor problem, Hydraulic lift issue
- Thread starter JC-jetro
- Start date
- Views: 78863
OP
JC-jetro
Elite Member
Scott,
This is getting ridiculous by now, but we'll find it. Please look at the pic below. There is ball check and spring to keep the shock load in control for the 3 point. Let's say you have a very heavy implement hanging in the back and you are driving on bumpy terrain. The kinetic energy produced at the 3 point due to weigh and it's motion can magnify the hyd pressure to the point that might damage the seal. The mechanism on right side of where you have the gauge will bleed some pressure off to avoid shock load, same as a pressure relief valve. please take them off and see if you get any oil coming out of there. Make sure not to mess up the order of ball and springs. By the way manipulate lift arm up and down while you are checking the flow. if you don't get oil then pump or spool might be bad.
JC,
OP
JC-jetro
Elite Member
Hey Scott,
We eliminated all the easy stuff that did not need a lot of intervention. We established oil coming out of relief device on post #41 with spring and poppet removed. I am not sure about quality of oil flow. What I mean is you have some flow but are you able to maintain any head pressure? It might be as the pump is pumping but it internally leaks and by passes the flow internally. The pump is a positive displacement gear pump but it does have an over pressure by pass so the pump would not self destruct. Although this is not sustainable as a lot of heat is generated. That is one possibility. The second is that the pressure relief is bypassing all the flow before it gets to the spool. The 3rd possibility is that spool vale is stuck at diverting all flow back to diffy. in your 3 point and another there is a feed back rod on the 3 point that bring spool to neutral position. when max height of arm is achieved then feed back move the spool in neutral position where In that fix all the flow is diverted to diffy and non goes to lift piston. Youu verified on post #43 there was no flow so either there was no flow to the spool or all of it got diverted. couple of questions here,
1-did you manipulate the lift arm handle as you were testing the flow?
2- briefly refresh series of event leading to this to see if there is any tell tale sign. How confident are you with the pump overhaul?
3- how confident are you with suction screen cleaning ?
I am sure you have an air compressor. On mine I have a discharge nozzle that is rubber tipped and is big enough. I would want to pressurize the open port on post #41. I might have to use a towel to keep it a bit tight, I would then check to see if I get any air pressure at the outlet on post #43.
Messing with the spool should be the absolute last resort. The thing is with a lack of quality flow good or bad spool would do pretty much the same. I wished I asked you to keep proper eye protection and rubber glove or somehow block the opening on the relief device by some rubber plug and test the flow and see what kind of pressure it develops.I wondered if you can make any pressure at all. Flow is not sign of pressure. Flow against the spring causes pressure. Let me know.
JC,
ps. another crazy idea, if you remove the lift cylinder, piston and lift cylinder head and start your tractor you should see oil gushing internally from the spool in the diffy or outlet port of that connect to the cylinder head. if no flow, them pump is very weak.
Just add a few pics of feed back arm to bring the Spool to Neutral position.
1st picture is the spool valve inside of diffy cover. I neutral position all the oil will be splashed back into diffy.
2nd pic is the cylinder head. notice 3 holes there, the middle is rate of return adjustment on 3 point. the one to the left of it where the piston get it's oil to move the piston .
3rd is the shock relief I was talking about. that is out side of the cylinder and it squirts some oil in to diffy to avoid shock loading when you carry something heavy on a bumpy terrain.
Last edited:
If you have any other ideas based on above, let me know and I'll try that as well. Thanks for the help!
Scott
OP
JC-jetro
Elite Member
Scott,
Please let me know what you have done lately. Can you answer to question on #44 thread. anything else you might have done. All I know we have flow from the banjo fitting n the discharge of the pump.Between the level of oil in the diffy in comparison to pump inlet is only few inches of lift,pipe pressure drop on the suction is not much . Having oil coming out of the gear pump is good but it is not all inclusive that the pump can make head pressure.
JC,
Please let me know what you have done lately. Can you answer to question on #44 thread. anything else you might have done. All I know we have flow from the banjo fitting n the discharge of the pump.Between the level of oil in the diffy in comparison to pump inlet is only few inches of lift,pipe pressure drop on the suction is not much . Having oil coming out of the gear pump is good but it is not all inclusive that the pump can make head pressure.
JC,
Last edited:
I took a break from this for a few weeks. Decided to dive into it again today. I did remove the lift cylinder, started the tractor to see how much flow I was getting in there. I'm not sure if it's normal, but it has alot of flow. The spool valve is covered with oil coming down over it. I've moved the 3 point up and down while its running. Zero resistance. As I said before, the tractor is my dads, so I'm not sure the events that led up to it not working. He says it quit working one day. The tractor doesn't get used much though and it sat outside for many years. My dads fairly mechanically inclined. I trust he cleaned the screen well.
OP
JC-jetro
Elite Member
Scott,
That is good. What it is telling me is the pump is pumping, flow is not by passing the relief device and it is dumping at the spool. The fact that you don't have resistance is that cylinder/piston was not there to collect the oil and causes pressure against the 3 point. Let me be sure, you ran that tractor with the cover removed and tested the flow with it removed? correct? if that is the case I would do it again and manipulated the spool and hope that something was blocking the passage ways in the spool valve and hope you get rid of contaminants like passing "kidney stone". The thick rod that you see , make sure it is inside the cylinder and piston is riding on it when you put it together.. Movement of the piston pushes the rod back and forth and that causes the shaft it is attached to to rotate and then lifting of the arm.
report back.
Ok, I was messing with some other projects and finally came back around to this.
I started it, moved the 3 point up and down several times with the cover off. No change.
Im sure the rod is going into the cylinder, my hand is actually small enough to fit inside the tube and guide it.
Any ideas beyond this?
Thanks for the help!
Scott
I started it, moved the 3 point up and down several times with the cover off. No change.
Im sure the rod is going into the cylinder, my hand is actually small enough to fit inside the tube and guide it.
Any ideas beyond this?
Thanks for the help!
Scott
OP
JC-jetro
Elite Member
Scott, One last thing, there is a knob right on the lift cylinder head and below the seat. That knob controls the rate of return of the lift arm. If that knob is all the way closed then you can lift the arm up but can not bring the arm down. Rotate the knob CCW to see if your 3 point start working.Look at the attached picture.
JC
