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MVP not holding position

Discussion in 'Western Plows Discussion' started by 01lariat, Dec 23, 2010.

  1. 01lariat

    01lariat Member
    Messages: 96

    Ok it probably has been posted before, but I didn't see it.

    My MVP doesn't stay put. It's mainly back dragging is the worst, but also pushing, slightly. It seems to be most noticeable on the damaged wing, that was struck by a car I guess. I suppose one or more valves releave or something under pressure.

    Which ones do what?
    Any adjustments to these valves?
    Rebuildable or just replace?
    Something else the problem?

    I suppose the cyl could internally leak by, but they seem GTG. No external leaks anywhere. New Western fluid.

  2. 01lariat

    01lariat Member
    Messages: 96

    No one? Here is what I noticed today. Seems there is plenty of play of the mounts both sides of the cylinders. That I didn't realize was there and I'll address that this week. Just some wear. However watching the rams when I push hard on the wings it appears like there is air in the system. Does air not work itself out with operation? I can see the rams move when I throw my weight against the wings. If there isn't any air they shouldn't move to me, untill a pressure relief allows it to, that is
    Last edited: Dec 26, 2010

    DGODGR Senior Member
    from s/w co
    Messages: 641

    You haven't said how old or how many hours are on the plow. It may be helpful. Do you have another (known to be in good condition) Western plow to see if the cylinders act the same way when you push on the end of the blade. The pin and bushing wear may be the problem (or part of it) but the fact that it's present may be an indicator to look elswhere too. I own an 8.5' MVP and an 8' Pro Plus. I bought the MVP used (slightly IMO) and the PP new. The PP is on it's 6th season and I just mounted the MVP about a week ago (I've only used one time). To me the MVP seems to be a little "sloppy" compared to the PP. I have never pushed on the ends of the blades to see if one will drift more than the other, and quite frankly I can't really think of a good reason why they would be different (if both were in good order) unless they were substantially different lengths. IMO if the problem was in the valve you would be able to push the blade to the stops. The compression in the cylinder, that you are witnessing, may be related to the cross over relief and the fact that the hydraulic system is not under pressure (like when the pump is running). It may also have to do with the oil getting compressed before the cylinder can resist the forces that you are applying. If the cylinder is drifting during operation I would suspect the relief valves (I assume they are a stack of washers if they are like most other hydraulic systems). I don't know, for sure, if they are adjustable but since most system are, I would think you have good odds that yours can be adjusted too. I'm not sure how you will set them correctly without gauges. Worn cylinder packing would be another thing to suspect. The abscense of external leakage, at the cylinder, does not eliminate the cylinder from suspicion. Internal oil bypass (oil passing from one side of the piston to the other) may be causing your problem. You can test the piston seals pretty easily:
    Run the cylinder to the fully extended or retracted position (it doesn't matter which, you will need to check it at both positions). Have something available to catch any hydraulic oil that may leak. Disconnect the hose that will return oil to the resevoir if you are trying to move the cylinder in the direction that you had already set it to (if it's extended, try to extend it farther or vice versa). If a little bit of oil comes out of the open fitting you are probably OK. If a lot comes out than you need to either rebuild that cylinder or replace it. Be sure to run it in the other direction if no oil comes out. I have seen the pistons leak in only one direction so be sure to check both. I would also check both cylinders (both directions of course). Any hydraulic repair shop can perform these tests, and should be able to repair them if required. The cost should not be much. If they turn out to be the problem (the cylinders) than I would see how much it would cost to buy new ones (I think they are only about $170 ea), and decide, from there, how much you would spend to repair the ones that you have (any reputable hydraulic repair shop would be able to provide an estimate before doing any work). I'm not a mechanic, and I'm sorry that I can't give you any more specific info than that. With no other replies I think that this can, at least, get you started in the right direction. Good luck, and keep us posted.
  4. TurboSam

    TurboSam Junior Member
    Messages: 9

    I had a similar problem with one of the original MVP from about 12 or so years ago. about 5-6 years ago it starting loosing position, and after trying pretty much everything to fix it, and after a new pump (that did temporarily solve the problem) we just said "the hell with it" and put a solid cutting edge on it and made it function like a standard plow.
  5. 01lariat

    01lariat Member
    Messages: 96

    Year unknown. It is an ultramount prior to nighthawks. Old uni-mount didn't move at all. That is what I'm going by. I'll look into it this week.
  6. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    Here is a pdf assuming it is a "ultramount" and not a "unimount". Download the pdf (easier to read) Look on pages 57-58. This is the mechanic's guide.

    This is the manual.....Look on page 95, it will tell you how to get the air out of the system

    Looking at your post, it really doesn't explain enough.. just not enough information, on the plow (what kind) or no information on what kind of vehicle the plow is attach..

    Now if you would of said for example "right wing extends, then wing drifts back ", I would suggest to take a look at S1, and S10 valves to see if there is movement, or their bent, or stuck, or even if there something blocking the passage way.. But I can't because there not enough info. One thing I did read is the "wing is damage", but doesn't say which wing? Here I could suggest ( let say right wing) the "relief valve" (ram) ps rod might be damage. Or the "check valve" (ram) ps base might be damage.

    Download the PDF's and look at them........Let us know what happen so we can further assist you with your problem..
    Last edited: Dec 27, 2010