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Subject: Another hydraulic 3 point hitch question

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Max    Posted 05-14-2017 at 18:05:51 [URL] [DELETE]        [Reply] [Email]  
  • Another hydraulic 3 point hitch question
  • Hello All:

    Need your infinite wisdom regarding my Ford 1948 8n.

    The hydraulics on my tractor are a bit tired. Depress the clutch or turn off the machine with an implement raised, and it will come to ground within 15-20 seconds.

    I was discing a small field last year when the fluid for the three point hitch ran dry on the dip stick. I topped up the fluid but could not get the implement to raise up. At best, it would just lift the implement enough to bounce and skip it along the ground while driving.

    If I took the implement off, the arms of the three point hitch would raise to the top.

    Parked the tractor for a later look.

    Finally pulled the old girl up and changed all the oils. Engaged the 3 point hitch with no load. up go the arms. Attach the discer and again, just barely of the ground. more like taking up the slack than getting it off the ground.

    Grabbed my air compressor, removed the dip stick for the 3 point hitch and stuck the nozzle in the hole and gave it some air. While blowing air, I raised and lowered the hitch with the discer on. No change.

    On my tractor, the top link rocker has three holes in it. I always attach the top link to the bottom hole. On a lark, I moved the top link to the upper hole. I engage the 3 point hitch and my pump comes to life growling low and up goes the discer. I try to lower the discer and nothing. Turn the machine off and down comes the discer. This happens three more times.

    the fourth time, I raise the discer and it goes to the top and then drops to the ground. And goes to the top and comes to the ground. All while the lever is engaged in the up most position. It goes up and down like this four more times before I turn off the tractor.

    Start the tractor again and now I have control of the implement. But not for long. Now we are back to the beginning again where I can just barely get it off the ground.

    So, off I go to disc a small field and, up goes the implement. In the fie, it works intermittently, going to the top or just barely off the ground.

    After discing the field, back to the house and I have spent the last two days researching the problem.

    I will be taking the cover off to look at the hydraulics when it stops raining.

    From what I've read, it could be anything from a worn relief valve to a scored cylinder and/or piston, loose control spring, stuck control valve, pump check valve, stuck inlet and/or outlet valves or worn quadrant draft control pin.

    Can someone please tell me what foul demon has possessed my poor three point hitch or am I going to have to do an exorcism in the form of a complete tear down of the pump and hydraulics?

    As always, your help is greatly appreciated.

    Kind regards,


    Den N Ms    Posted 05-15-2017 at 12:24:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Another hydraulic 3 point hitch question
  • Max ,Here is some good info to follow for repairing your lift.

    Stumpy(NH)    Posted 05-15-2017 at 06:37:53 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Another hydraulic 3 point hitch question
  • To me it sounds like worn mechanical linkage is the main trouble, secondary, oil leakage at either relief valve or piston.

    You're right to take the cover off. Check the stand pipe that goes up the right side of the case, they rust. I had this problem years ago on my 8N


    Max    Posted 05-16-2017 at 22:30:49 [URL] [DELETE]        [Reply] [Email]  
  • Re: Another hydraulic 3 point hitch question
  • Did a little checking out of the hydraulics today. Started with the simple one. Hooked up an implement to the 3 point hitch and raised it up. Surprisingly it went all the way up. However, after a couple of tries moving the implement up and down, when I left the lever in the up position, the implement would rise to the top and then fall to the ground, only to rise to the top again and repeat the process until I lowered the control lever. So I'm thinking stuck valve in the pump or possible scored cylinder or blown cylinder rings?

    Prior to raising the implement to fully raised position, I moved the top link to the lowest hole on the top link rocker and, when the implement was up, I did the three finger check on the main control spring. Shouldn't turn if implement raised. Never mind three fingers, I could spin it freely with one finger; my baby finger.

    So I'm thinking tighten the draft control yoke and new draft control spring plate with pin?

    Tomorrow I take off the side plates to get a look at the boiler room, LOL.



    Max    Posted 05-17-2017 at 20:10:11 [URL] [DELETE]        [Reply] [Email]  
  • Re: Another hydraulic 3 point hitch question
  • Yoke and spring plate with pin

    Busted plunger

    Homemade tractor forks

    Cylinder and piston

    Piston rod

    Max    Posted 05-17-2017 at 23:23:12 [URL] [DELETE]        [Reply] [Email]  
  • Re: Another hydraulic 3 point hitch question
  • As you can see by the pics< I started tearing down my hydraulics today.

    Started by removing the top link rocker and got a shock when I saw the wear on the yoke. Figured I'd take the yoke off and weld up the divet and reuse it.

    Instead, I broke the draft control plunger in an effort to unscrew the yoke from it. You can also see what bad shape the draft control spring plate with pin is in. Oh, and no spring seat. No wonder I was getting no lift function.

    Since I broke the plunger, I removed the hydraulic top cover to get a look at the piston and cylinder. Both look to be in great shape but the piston had no leather washer. Might explain why it didn't hold pressure.

    I will get a new NAA piston. Better sealing from what I read.

    Notice the flat spot on the piston rod. Is it supposed to be like that? Should I get a new one?

    Next stop, drop the hydraulic pump.



    Max    Posted 05-22-2017 at 21:57:17 [URL] [DELETE]        [Reply] [Email]  
  • hydraulic pump tear down with pics
  • Another beautiful day so I thought I'd start work on the hydraulic pump.

    Cleaned the pump with diesel fuel, a wire brush and some paper towel.

    Pulled the relief valve, the exhaust control valve and the intake control valve.

    More to come when my parts arrive.



    I have a new relief valve on order. Do the intake and exhaust control valves need replacing and if so, where can I get new ones? I measured the intake and exhaust control valves and they both measure .592" and have a beautiful fit in the chambers. Chambers look good with no scoring.

    Pulled the valve clamps to get a look at the inlet and outlet valves. Glad I've got new ones on order.

    This was the yoke when I pulled it apart.

    After a little welding and some paint and, she is ready to go back into service

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