Posted by Terry Larrow on July 29, 2012 at 14:48:12 from (76.226.202.25):
Question: I have excessive hydraulic pressure in the lift all pump in my 1951 Farmhall H tractor with a late model 800 psi lift all belly pump that runs a hydraulic cylinder on my 3 point hitch. When the pump is lifting the load, the gage reads 800 psi, when it gets to the end of the stroke of the cylinder it rapidly rises to 3200 psi. At this point the relief valve cap pushes up and releases the locking lever and moves to the bypass position. The pressure on the cylinder remains at 3200 psi which makes it difficult to release the check values for the lift cylinder. I have removed the pump and the oil was clean as well as the inside of the pump. I checked the gears and gear housing and endplates for wear. All the parts are within factory specification with little or no wear. I also installed new bearings in the gears. I installed a new input shaft seal. I have removed the old balls on the check valves and used them to lap the seats and then installed new balls on the check valves. I disassembled the relief valve used the old ball to relap the seat and installed a new ball and spring. I ordered the new spring from International using the part number from the Farmhall H parts book. It only showed one relief spring available. I compared the old spring with the new spring and they are identical. I have read that the kick out pressure for the relief valve should be 800 to 900 pounds. All the levers, cams and latches move freely and show no signs of wear. I used high trans oil to fill the reservoir. I am concerned this high pressure will cause damage to the pump housing. Does anyone have any thoughts on what I can do to resolve this problem?
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