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MVP Plus lift ram pushing gland nut out

Discussion in 'Western Plows Discussion' started by mishnick, Mar 2, 2011.

  1. mishnick

    mishnick 2000 Club Member
    Messages: 2,353

    Today I worked on an MVP Plus that had (for the second time) pushed the gland nut right out of the top of the lift ram. Fortunately it just ripped the threads of the cast gland nut and did little damage to the cylinder threads. So I cleaned out the bits of threads that remained in the ram and put together again, with a new nut & seals of course. Initially I thought there must be a pressure relief valve that had failed because the owner said it happened previously. So I looked at the mechanic's guide and learned that there is no PRV on that circuit. I am assuming that this is because there is no reason to expect any impact to cause overpressure.

    Having questioned the owner a bit more he explained that in both cases he put the cold truck & plow in a warm garage and parked it overnight (leaving the plow elevated to the max). Now here is my hypotheses.... tell me if I am crazy or is this something that actually happens.....

    I suspect that the cold fluid warmed up and expanded forcing the gland nut out because that was the weakest point. Since there is no PRV it had nowhere else to go right? Now if he had dropped the plow to the floor the expansion would have just lifted the blade a bit or tightened the chain some. What do "all yall" think? Am I crazy?
  2. Tony350

    Tony350 Senior Member
    Messages: 546

    That kinda makes sense to me. Makes sense that there isn't any releif valve on the lift ram can't see a shock load hitting it. I can't think of anything else but I am no mechanic either. I would tell the customer to drop it or make the aframe isn't bottomed out into the light bar and see what happens.

    Have you called western what did they say? Kinda intrigued let us know if you come to a conclusion.
  3. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    Theory, fluid is being built up and no where else to escape except to the weakest point of entry, or unless is there was a way to relieve the pressure.

    The plow is being left in the raise position (don't ask me why anyone would do that when you put the truck and plow to sleep for the night). At the same time, the remaining rams still have fluid left inside each cylinders. Let say for argument sake, the plow was set into the raise position, then the customer decided to hit the button fast to kick the blade to the right (which now has pressure inside the ram). Now the check valve should hold the fluid in the base of the ram(right). Instead the check valve for reason decide to not do it job and leak a little. Then a little more. The fluid leaking has to find some were to go, so the closes point would be the lift ram. The fluid goes through the channel into the ram. The ram is so far extended and building pressure that is has no where to go but up and through the gland nut, and with that amount of pressure ripping the weak threads apart.

    Possible causes

    A) pump relief valve is not doing it job
    B) there is a check valve problem somewhere
    C) Pump housing is defected
    D) (can't believe I am going to say this) The customer has the controller wire into a "hot lag (constant power)"
    in the fusebox, and the controller has a malfunction there is a glitch in the pc board that has slight pressure on the raise position. And when the truck is sitting, and the plow is in the raise position, the switch on the pc board decides to click on and off by itself with out no control of the operator..
    E) or there is more to the story and the customer is not tell you all of it......


    Just a thought

    Last edited: Mar 3, 2011