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HYD01639 Pressure Relief Valve Adjustment - Boss V-PLow

Discussion in 'Boss Plows Discussion' started by MountainMog, Feb 14, 2011.

  1. MountainMog

    MountainMog Junior Member
    Messages: 13

    I've been experiencing the infamous "my plow wings retract too easily" problem, so I removed one of the HYD01639 Angle Relief Valves to investigate. I'm no stranger to hydraulics, and I have gauges, so I'm seeking advice in how to calibrate these relief valves to the 2800psi spec.

    Problem is I don't see any screw adjustment. I'm assuming that would be at the rear of the internal spring, but how do I access it? Does the end of the valve body where the Allen wrench would go un-screw to reveal the adjustment screw? I tried that with the valve body clamped in a vice but it didn't want to move so I'm assuming the valve body is one piece?

    Maybe the brass tip is removed for the adjustment?

    Also when I removed the valve from the manifold body the large O-ring which had hardened over the years (it's a 10 year old plow) disintegrated and needs to be replaced. The 2 small O-rings on the brass tip should be replaced as well, so is there a seal kit available for this?

    BTW, this is my first post to the forum, looks like a great site! My plow is mounted on a Mercedes Unimog hence my user name.:)

    Thanks for your help!
    ~Frank

    HYD01639-A.jpg

    HYD01639-B.jpg

    HYD01639-O-Ring.jpg
     
  2. RBRONKEMA GHTFD

    RBRONKEMA GHTFD 2000 Club Member
    Messages: 2,592

    Welcome to plowsite. I am sure someon would know. I hate just telling you to go to someone because I always try to help people. But I am going to say that you should talk to B&B. He is very knowlegeable about this stuff. 1 questions is why do you want to change the relief valve psi? I like the fact it wont wreck your plow if you hit something hard. Well some what anyway.
     
  3. MountainMog

    MountainMog Junior Member
    Messages: 13

    I don't want to just arbitrarily change the PSI setting, I just want to make sure it's up to specs. After ten years relief valve springs can "get tired" and lose their tension, so it may be necessary to adjust the valve to get it back to 2800psi. The plow wings retract way to easily.

    BTW, Thanks for the welcome! :)
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The adjustment screw is behind the allen cap on the face of the valve. Remove it and you'll see another allen down in the valve and that is your adjustment screw. Turning clockwise increase relief pressure and counter obviously does the opposite. Be sure to use a gauge to make the adjustments.
     
  5. MountainMog

    MountainMog Junior Member
    Messages: 13

    B&B, Thanks for confirming that. I knew that was the way it should be, but that end cap is really stuck on there. I had the valve clamped in a vice and I couldn't break it free. I'll make another attempt today and either tap the Allen wrench with a hammer to break it free or use a 'cheater' on the Allen wrench. Maybe a little PB Blaster is needed here.

    2 questions:

    1]. Is there a seal kit available for this valve? I called three authorized distributors in Denver and none of them could find a listing for that. All they could offer was a new valve ($65). I'm sure I can find a replacement for the large O-ring, but the 2 small ones on the brass tip may be hard to find. One has a square cross section, and the other has a round cross section. Any suggestions for finding a match for those?

    2]. What's the best way to test with a gauge? I'm thinking insert the gauge between the angle cylinder and hose, but will the pump achieve 2800psi? I've read several threads on this forum referring to pump pressures in the 2200-2300 psi range. What is the psi setting for the pump manifold pressure relief valve (HYD01693)?

    It also occurred to me to place the end of one of the wings against a tree (I've got a million pine trees up here) and gently drive forward until the wing moves back and note the pressure on the gauge at the moment the wing breaks free and moves back.

    What do you think is the best way?
     
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If you're finding worn/hard o-rings (not uncommon on ten tear old hydros) I'd recommend replacing them all to save yourself periodic headaches and downtime, not just those on the relief valves. You can purchase a complete valve body only seal kit from Boss.

    When checking/adjusting wing relief pressure, the pump relief pressure is irrelevant since it has nothing to do with the wing reliefs. Tee your gauge into a wing hose and force the wing back (your tree method would be fine) and then adjust the relief for that wing accordingly.

    If you wish to also check pump relief (always a good seasonal PM check) tee your gauge into the lift ram hose, lift the plow and hold the pump against relief. Then make any adjustments to that as needed. Should be set around 2300-2400.
     
  7. MountainMog

    MountainMog Junior Member
    Messages: 13

    Thanks B&B, I'll definitely get the complete valve body seal kit. Would you happen to know the part #?

    I finally got the cap off, it took an Allen socket on a 2' breaker bar to break that sucker loose with the valve body clamped in a vice. I never would have gotten that off with it still in the plow.

    One other question: When I got the cap off I noticed the cavity under cap was filled with oil. Is this normal, or should the oil not be bypassing the relief piston?

    I'll be putting gauges on the plow tomorrow, I'll let you know what I find out.

    Cheers,
    ~Frank

    HYD01639-C.jpg

    HYD01639-D.jpg
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Seal kit p/n MSC03715. The end plugs can be a real bear to break loose sometimes, I've twisted wrenches off in them before. It's normal for there to be fluid in the relief body, bypass fluid and pressure flows though it. It wouldn't require an o-ring under the cap and it be so tight otherwise. Good luck with your checks.
     
  9. MountainMog

    MountainMog Junior Member
    Messages: 13

    Thanks for the part number B&B, I'll get that ordered ASAP. I'll be doing a complete overhaul of the plow after this season, so I'll wait until then to replace all the O-rings. I'll get a seal kit for the power unit as well and replace the strainers as well (part # HYD01670).

    In the meantime, could you give me the part # just for the relief valve? I can't seem to find it.

    Again I appreciate your help!

    BTW, I got the following information from one of the local Boss dealers, thought it might be useful to anyone who passes this way...

    HYD01639 Pressure Relief Valve Factory setting: 2800psi.
    Turning clockwise increases pressure to:
    1/4 turn = 2888psi
    1/2 turn = 2978psi
    3/4 turn = 3071psi
    1 turn = 3167psi

    .
     
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    HYD07028 would be the relief seal kit if memory serves me correctly.


    Yes a 1/4 turn is aprox 100PSI but don't use the turn method to make an adjustment as it's based on a 2800PSI initial setting, which often isn't an accurate assumption. A gauge must be used.
     
  11. MountainMog

    MountainMog Junior Member
    Messages: 13

    Oh yeah, I wouldn't attempt this without a gauge. I have other heavy equipment and I'm no stranger to hydraulics and using a gauge.

    I decided the idea of using a tree against the wings while moving the truck was just too crude of a method. With the truck in motion it would just be too difficult to watch the gauge, and it would also take the coordinated efforts of two people to accomplish that. So I used a come-along instead. The way my plow is mounted on the Unimog made this easy. The photos tell the story.

    The pump pressure was at 2350 psi (within specs), and sometimes a little higher with the gauge inserted into the lift cylinder line with the pump motor running. However the pressure relief valves on both wings cut in at around 2300-2400psi., way too low. It took a little over a half turn of clockwise adjustment on both the right and left angle pressure relief valves to achieve the 2800psi spec. So I guess the relief valve springs do get a little tired after 10 years! :eek:

    At any rate I won't really know what the improvement will be until the next time it snows, but hopefully the wings won't fold back as easily as they have been.

    Here's some pics showing the method I came up with to calibrate my angle pressure relief valves:

    Here's the setup I used to move the wings to check the angle relief pressure:
    Test-Setup.jpg

    Gauge teed into the lift cylinder line showing the pump pressure:
    Pump-Pressure.jpg

    Here's the gauge teed into the right angle cylinder line, before the actual test:
    Angle-Pressure-Setup.jpg

    And here's a photo of my Mog:
    Unimog-Boss.jpg

    Pump-Pressure.jpg

    Angle-Pressure-Setup.jpg

    Unimog-Boss.jpg

    Test-Setup.jpg
     
  12. MountainMog

    MountainMog Junior Member
    Messages: 13

    That part # says it's for a Bi-Directional Relief Valve Seal Kit. Would that be correct for a V-Plow? Wouldn't Bi-Directional relate to a cross over relief valve for a straight blade plow?

    [​IMG]
     
  13. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Don't allow the description to mislead you, it is the correct one.



    Very nice rig by the way. :salute:
     
  14. MountainMog

    MountainMog Junior Member
    Messages: 13

    Well, I'll take your word for it... your definitely the resident Boss plow Guru here! Thumbs Up

    I also was wondering why the package has at least 7 O-rings in it when the angle relief valves only have 4 O-rings (the 2 small ones, the large one that seals the valve to the manifold body and the O-ring on the cap).

    I guess it's more or less a 'universal' seal kit that fits many different Boss relief valves?

    BTW B&B, I really wish to thank you for your help, it really is appreciated!
     
  15. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Your thinking is correct Frank, the "kit" works on various relief valves therefore there's a couple extra parts yours won't require, so you're still good to go.


    And happy to assist. :waving:
     
  16. Kmo

    Kmo Junior Member
    Messages: 11

    RT-I valve?

    Hi, New to the discussion but I have a related question and the pictures are great here.

    I have an RT-I on an '89 Chev. 1-ton and also having issues with the relief valve, I assume as both wings are a little weak in heavy snow. I think there is only one relief valve on that early model, right? Would the same info and seal kit work?

    I know its a partly unsupported model and parts are hard to find, but had no choice last winter.
     
  17. MountainMog

    MountainMog Junior Member
    Messages: 13

    Had to log on to see who revived my old thread!

    Kmo, sorry to say I have no info for you, but I'm sure B&B will be along soon to answer your questions...
     
  18. Kmo

    Kmo Junior Member
    Messages: 11

    Thanks for checking in. And for the great pictures - very helpful.
     
  19. Kmo

    Kmo Junior Member
    Messages: 11


    By the way, a neighbor has a UniMog that is in disrepair and the main operator passed away. I have mechanical skills and could perhaps work something out with the family to get it running again. How tough are they to get into shape? Any advice?
     
  20. MountainMog

    MountainMog Junior Member
    Messages: 13

    If you could get that Mog for a good price, I'd go for it! They're amazing vehicles, made by Mercedes, most have 20 speed trannys, front and rear lockers, and enough ground clearance for the differentials to drive over a 5 gallon bucket! If you want to learn more about Unimogs, you might want to check out the Benzworld Unimog Forum.
    If your serious about purchasing the neighbors Mog, you might want to sign up on the Benzworld forum and upload some pics of the Mog and you'll get the answers you need as to what model it is, what it might be worth in it's current condition, etc. The members there are very knowledgeable, friendly and helpful!

    Where in Colorado are you located?