JD4240 power steering heavy
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Thread: JD4240 power steering heavy

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    JD4240 power steering heavy

    Working on a friends JD4240 that has heavy power steering. The steering motor seals have been replaced, the steering valve has been renewed but still no luck. We have removed the metering pump on the steering column but it does not seem to be worn much at all. Several minor radial marks only. I am wondering if there is sufficient oil getting to the system from the oil regulating valve. The hose has been replaced some time ago but it seems to be a small diameter hose that may restrict the oil flow. I don't want to replace the metering pump $2300 new if it is OK. Talked to the dealer but no new leads. Has anyone any suggestions on what may be the cause. I am thinking of rubbing back the 2 surfaces of the metering pump with fine emery paper and putting everything back together with new seals, shims, etc. Any suggestions are appreciated.

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    Welcome to GTT
    How long since hyd filter was changed & sump screen checked/cleaned? Has hyd stand-by pressure been checked lately? I'd set stand-by pressure at 2400 psi. Do any hyd functions appear to be hotter than other hyd functions? Have frt axle spindle grease fittings been greased regularly??
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    flyweight's Avatar
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    Did you replace the needle bearing(#7) and washers(#6) ? I've replaced many of these because of a hard steering complaint.

    Inspect the check-valve(#30) for foreign material. Replace is needed.

    Note: If you remove plates(#20) and spring(#21) you'll have super-easy power steering.

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    Michael

    '84 JD 750
    '08 JD Z445
    '71 JD 15 Chainsaw
    And a bunch of other stuff.


    " If there's no one around to smell me, do I really stink"?
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    Heavy power steering

    Thanks for those that have suggested remedies. Filters and pressures have been checked. I have noticed that the pressure line from pressure control valve to metering pump has been changed at some time. I also notice that is is a 1/4" hose with restrictions smaller at the fittings. Specification of correct part show hose should have 9.5mm diameter hose hence this is much smaller. Wondering if there is a pressure drop in that line that is causing the heavy steering. The steering was always heavy when starting but improved after a time when the tractor warmed up.

    On one reply it was suggested to remove the spring and plate #21 and #20. What does that do and will it change anything else?

    On dismantling the metering pump there are some circular scores on the end plates that correspond to the outside of the gears. You can feel them with your finger nail but they don't seem to be too bad. No other wear evident in gears or centre plate.
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    JD4240 power steering heavy

    Following up on the suggestions given, I have noticed that the needle thrust bearing is not there. It must have disintegrated and only the 2 thrust washers and the needle retainer was there. I will replace these. That may increase the weight of the steering but would think it would be heavy all the time. Maybe a combination of that extra load caused by friction and also restricted pressure hydraulic line is my problem. As oil warms it would become thinner and more oil may get to metering valve. Comments appreciated.
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    flyweight's Avatar
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    Quote Originally Posted by linlee View Post
    On one reply it was suggested to remove the spring and plate #21 and #20. What does that do and will it change anything else?
    The plates and spring are installed to cause a slight drag in the gear. With this missing, the steering wheel will spin freely, like a Roulette Wheel.


    Quote Originally Posted by linlee View Post
    Following up on the suggestions given, I have noticed that the needle thrust bearing is not there. It must have disintegrated and only the 2 thrust washers and the needle retainer was there. I will replace these. That may increase the weight of the steering but would think it would be heavy all the time. Maybe a combination of that extra load caused by friction and also restricted pressure hydraulic line is my problem. As oil warms it would become thinner and more oil may get to metering valve. Comments appreciated.
    The missing needle bearing is most likely the problem with hard steering.
    When the tractor is started and steering supplied oil pressure is pumped to the metering valve, oil pushes the steering shaft upward. The needle bearing is installed to help reduce the friction.

    Note: Do a test.
    Place the palm of your hand over the center of the steering wheel. Start the tractor. As the hydraulic pressure builds, you will feel the steering wheel being pushed upward.
    Last edited by flyweight; 10-31-2017 at 07:46 AM.
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    Michael

    '84 JD 750
    '08 JD Z445
    '71 JD 15 Chainsaw
    And a bunch of other stuff.


    " If there's no one around to smell me, do I really stink"?
    - John Wells - Brewster County, West Texas.










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    linlee (10-31-2017)

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