88 Hydraulic Problem

TASO

Member
We did a lot of rework on our 88 diesel. The original hydraulics were the electric controled switches and the pump centerplate was cracked. So we had the pump rebuilt with new bearings, seals and centerplate. Then we bought a newer reservoir with levers off of Ebay. We put everything together and checked pressure. We have over 1800 psi.But when we connected to an implement, we can only raise or extend the cylinder. We cannot retract or lower. We noticed that when working the levers, we have a lot of travel upwards and the relief valve will squeal at the end of the lever stroke. When operating the levers down, there is very little travel and no noise from the relief valve. We are puzzled as to why this is and what to do next. We use the tractor to ted hay with a four basket tedder with hydraulic fold and we need the hydraulics to work properly.
 
First things first... If you have purchased a double lever hydraulic unit it should have two valves inside. Plumb the hoses to the unused side and see what you have there. If the trouble persists then you either have purchased a damaged unit and it will need service or you have cylinder/hose/coupler troubles. Your restrictor screw in the down side might also be screwed in all the way. Not much else it can be, if the pump is putting out that kind of pressure. Most factory units only made 1000-1100 PSI when new. If the hydraulic unit is working right you should be able to lift a house with that kind of pressure! My 770 snaps a 9ft haybine up in 3 seconds. Good Luck! Ron
 
I recently had a similar problem on my 88 with the 3 point cylinder. I hooked the hydraulics to a spare cylinder and all worked well. I learned the problem was in the JD cylinder on my 3 point. Something with the depth control pin was locking the cyl in the up position. I change the cyl and the problem has not returned.
 
Thanks for all of the input. The reservoir holds ~6quarts and it is full. We tried 3 different cylinders with the same result. We also tried both levers.
We are going to pull the reservoir and levers off and start studying things over. The system acts like it is set up for single action.
 
You are correct. My sons gave me the dickens. They checked the pressure and wrote ~1300. My old eyes saw 1800. It is likely closer to 1200. We are going to remove the reservior and valves and go through the unit. We have another replacement unit if we can"t figure out what is going with this one.
Thanks for the input.
 
Got into the reservoir. The unit was purchased on Ebay and had wires going into the unit that were cut off. Selector valves were locked in one position by solenoids that we could not get to release. After unsuccessfully trying to power up the old wiring system from a battery, We just replaced the reservoir and selector valves from another spare unit we had just bought. We will have to continue to play with the other to see if we can get the solenoid to release. Should have checked it over more closely before putting in the tractor.
 

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