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ultramount mvp plus 8.5 lift ram will not stall up drops down as you drive

Discussion in 'Western Plows Discussion' started by howardg3, Feb 4, 2011.

  1. howardg3

    howardg3 Junior Member
    from name
    Messages: 20

    call my local dealer & he told me i needed to replace my S3 valve. I replace my S3 valve and it is not better & I also check to make that magnet was good & no short going to it, all was good. help
     
  2. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

  3. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    First you need to check the S2 valve as this is the only other valve that is exposed to the residual pressure from the lift ram. S2 leaking would allow fluid to slowly leak back through the pump.

    http://library.westernplows.com/ddcommon/dd_pdf/pdfs/27366.00_010107.pdf (Look at the schematic on page 35)

    Another thing to try is to lift the plow off the ground and then dissconnect all power sources to ensure there is no small amount of current partially opening the S3 valve. If the plow doesn't sink down with the cables unpluged from the truck then you need to look an electrical problem. I would put a voltmeter across the pins of the S3 valve and see if there is any voltage there at all. When activeated it will show 12 volts and when inactive there should be zero volts. If there is even one volt there when inactive you have an electrical problem.

    But check the S2 valve first as that is the most likely problem. You don't have any fluid leaking out of the black plastic covers do you? Or from the fitting with the cap on it (pressure test port) as a simple small leak on the lift ram circuit will allow the ram to leak down.
     
  4. fabcraftinc

    fabcraftinc Member
    Messages: 69

    I have a couple questions about this area of the manifold. The oil from the lift cylinder can flow back to tank two ways. One is through the S3 and the quill. The other is through a check valve and then through S2, referencing the MVP plus mechanics manual hydraulic schematic. Wouldn't the check valve have to fail first then cause the S2 to fail? Also, let's assume the check valve and S2 side is all good. If the S3 fails, is the quill fully "in", enough to hold the plow in the up position?
     
  5. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    Forget about the quill, oil can always pass by that otherwise the blade wouldn't drop. The quill is just a restriction to slow the drop speed. The ball check beside the quill opens to allow fluid around the quill restriction when the blade goes up so it moves fast. The check valve by S2 would have to fail for fluid to pass by S2 but since the ball and the S2 valve are one piece you need to pull the S2 to inspect that check valve. Last point... the quill is not a valve, just a restriction so screwing it all the way not seal tight and is not recommended because it could damage the quill needle.
     
  6. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    If I am reading you into correctly, your plow start to drop while your driving down the road?

    Here the function for the S2 and S3 valves.

    S2= raise, angle left, left retract, left extend
    S3 = raise, lower, V, scoop

    Do you have a problem with all the function listed above??

    As you can see, were missing a "S " vale that control one by itself even though another S valve control the same function. The "S1" control the "lower" function.(look on page #41)

    hold.jpg

    As for your questions, the diagram should speak for itself. You can check the P/O inlet check valve to make sure the spool is intact and nothing stopping it from functioning correctly.
    poilet.jpg

    As for the "Quill". It control the drop blade speed.

    Check the S1 valve..Do a test (look on pages #84,#87) to make sure it is spooling (movement).. Check the seal to make sure it not damage.


    Answer to your first question
    myschematic.jpg
    myelect.jpg

    myschematic.jpg

    myelect.jpg

    poilet.jpg

    hold.jpg
     
    Last edited: Feb 5, 2011
  7. fabcraftinc

    fabcraftinc Member
    Messages: 69

    so, on the hyraulic schematic, the check valve shown "above" the S2 is actually part of the S2. Now I know why those dashed lines are there! Learn something new everyday! Howardg, you know that first valve you took home.....
     
  8. fabcraftinc

    fabcraftinc Member
    Messages: 69

    Thank you mishnick
     
  9. howardg3

    howardg3 Junior Member
    from name
    Messages: 20

    I am already on it I am on my way to my friends house he has a spare one


    thank you verry much
     
  10. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683

    thanks mishnick for posting the schematics. not bad
     
  11. howardg3

    howardg3 Junior Member
    from name
    Messages: 20

    so far so good replace the s2 valve assy & seems to be staying up. the true test will be when it gets used for 7 to 9 hours. This is all new to me so I a learning as i go. I would like to thank (Twinman326, Fabcraftinc. & Mishnick for taking time out of you day to help me.
     
  12. fabcraftinc

    fabcraftinc Member
    Messages: 69

    do you see the S3 or S2 failing more to cause the blade to drop as in this case?
     
  13. mishnick

    mishnick 2000 Club Member
    Messages: 2,243

    The S3 valve would be the first thing I would have suggested you check based on the complaint, the first guy was right about that BUT when you said replacing that had no effect the S2 had to be it. Even then beyond that there is the remote possibility that there is a crack in the housing allowing fluid to leak from pressurized chambers back to the reservoir. All a fellow can do is the logical step by step process of elimination.

    By the way, I understood that this was an MVP plus right? You need to know that there is a difference between the plus and the regular version. The hydraulic schematic that twinman posted above is close but not exactly the same. The schematic shows a great sample of how the valve cartraige can contain both the main valve and the check valve in one.

    I wish I could pick out pages from the Western website and make them visible on the thread like twinman does. I also like the way he is able to make coloured highlights to bring attention to specific features. One of these days I will figure out how he is doing that....
     
  14. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Could have swapped the S3 with the S1 or S5, and swapped the S2 with the S4 to test before buying valves. But at least you'll know for next time.
     
  15. fabcraftinc

    fabcraftinc Member
    Messages: 69

    that is the beauty of having common valves in this system
     
  16. fabcraftinc

    fabcraftinc Member
    Messages: 69

    it is a MVP +... Thanks again
     
  17. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Just a shame they're not all the same like on some other brands. Less inventory and less chance of not having the correct one on hand.
     
  18. twinman326

    twinman326 PlowSite.com Addict
    Messages: 1,683