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580 Super L hydraulics leaking off

Discussion in 'Tractor/Loader/Backhoes' started by Trout Dad, Mar 13, 2020.

  1. Trout Dad

    Trout Dad New Member

    Joined:
    Dec 8, 2019
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    Location:
    Staunton
    Everything leaks off. Not just one 1 outrigger, boom or front bucket. The front bucket, outriggers, boom, everything. It did this from the time I bought it and was tolerable. It would take days for it to leak off enough that the boom would eventually touch the ground. Now it leaks off while running and enough that you can see it leaking down 6" in a minute! Not good.
    Is there a check valve or by-pass valve between the pump and the manifold? I'm going to rebuild the manifold but I sense it is another issue somewhere else.
    Any help would be great. Anyone have a hydraulic diagram or site where I can review the hydraulic system?

    Thx,
    Troutdad
     
  2. highwayghost

    highwayghost Senior Member

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    Occupation:
    Emissions Analyst
    Location:
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    How many hours on the machine? See hyd diagram. Main relief valve (#21) leaking??
     

    Attached Files:

    Last edited: Mar 13, 2020
  3. Trout Dad

    Trout Dad New Member

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    4400 hours. Yeah, leaks off running. Main relief valve #21. I tried to view the attachment, bunch a numbers.
     
  4. highwayghost

    highwayghost Senior Member

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    Right click and open with Adobe reader.
    With 4400 hrs have the cylinders that leak off ever been rebuilt? Do the wiper seals on the cylinder rod look good?
     
  5. LN Pipeline

    LN Pipeline Well-Known Member

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    Location:
    Montana, USA
    My guess is cylinder seals.
     
  6. Trout Dad

    Trout Dad New Member

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    Yeah, I know I have a couple that need rebuilt. I’ll try that first and the relief valve you mentioned. Thx so much.
     
  7. highwayghost

    highwayghost Senior Member

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    Look at the wiper seal on the cylinder rod. If it looks bad then it is very likely the inner seals are also bad. The cylinder could be leaking internally causing your leak down. Leaks may also show keeping the rod wet with fluid. If rebuild fixes one cylinder then it's more likely cylinders and possibly spool valves. Be sure your using the proper hydraulic fluid.
     
  8. melben

    melben Senior Member

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    Location:
    pennsylvania
    I have problems believing that piston seals are causing the loader leak down, if the valve is in good shape the piston can only move down far enough for the pressure to equalize on both sides of the cylinder then the cylinder will stop because there is more volume on the piston side than the rod side. The boom and dipper could because the weight of the boom or dipper is pulling the rod out and the leakage would go from the rod end to the piston end. While I have never seen that much wear in a valve in that few hours, I would suggest having it looked at, maybe someone in your area has the equipment to pump back against the valve to check secondaries. Maybe you have some o rings deteriorated in the valve cartridges. It will be interesting to find out what you discover. Again, if the cylinders that the rod push in to leak down leak all the way to the ground the oil is getting back through the valve somehow if there is no severe external leakage.
     
  9. LN Pipeline

    LN Pipeline Well-Known Member

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    Location:
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    Makes sense. I think this video is saying the same thing that you are.



    For some reason things don’t follow this logic in the real world. A fully raised loader will drift all the way to the ground with a bad piston seal.

    Almost all cylinder drift that I have encountered has been due to a leaking piston seal.

    That’s where I would start, mainly cause they are easy to test. I’ve posted this video before on testing hydraulic cylinders. It’s not my video.

     
  10. melben

    melben Senior Member

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    Respectfully, I spent my entire career in this field, if you look at it logically if the piston moves down and oil bypasses the packing and it has nowhere to go and cannot go back through the valve on the rod end pressure builds and equalizes on both sides of the piston and the rod stops, the real effect is that the surface area of the cylinder becomes simply the rod diameter, I have seen this many times and after you have spent as many hours 50+ years you will agree with me, now keep in mind the rod can pull out if enough pull is put on it as it will create a void in the butt end of the cylinder, that is why modern valves have a regeneration circuit built in to allow return oil back into the supply. The only way the rod can retract is if the rod end supply hose is loosened so the pressure created in the rod end caused by more volume of oil in the piston end than the rod end can accept causes the pressure buildup that keeps the rood from further retraction. I remind you, I spent my life ar this stuff. In my career I have had phone calls from Case Service personell to discuss hydraulic issues. When at my job I could find a leaky packing in a cylinder by heating the oil and feeling around the barrel for hot spots where the oil was bypassing, I did not need pumps, I found problems in bugged machines at service schools that the instructor said could not be found without a flowmeter. On a dual loader lift cylinder system a piston seal leak on one cylinder will allow about 4-6 inches of down drift before the pressures equalize after releasing the spool. Piston seal leakage can often be found by holding the hydraulics against relief with hot system oil and feeling the barrel where the piston is and the leak will be apparent by a hot spot on the barrel, on any of these problems your senses are your best friend. BTW I do believe in flowmeters for system diagnosis,in fact we flow tested all new backhoes and recorded the results as a baseline for future reference and it has bailed us out in a few instances.
     
    Last edited: Mar 16, 2020
    Tinkerer likes this.
  11. LN Pipeline

    LN Pipeline Well-Known Member

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    Location:
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    I’m not a mechanic, and I don’t work in a hydraulic shop. I joined the forum to ask questions.

    The first thing I responded with was “Makes sense”, and I posted a video that validated what you said, because it does in fact make sense.

    If you don’t think the guy should start with the simple/easy tests that would require only a few caps and plugs, that’s fine.

    I saw a several page argument on an ag forum a while back over this EXACT same thing. I’m not going to argue with you.

    His piston seals might be good...
     
    Last edited: Mar 16, 2020
  12. melben

    melben Senior Member

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    Location:
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    For a first timer caps and plugs are the place to start, Even later on they help out, Pascals Law goes into fluid behavior and it would do all persons interested to look at it, It is a Law, not to be violated, in the thing we are looking at I think you must agree that a leak on either side of the section that leaks down would be capable of causing drift down , a minor seal leak will allow it to seep down but a major transfer by the piston will not even allow it to lift.
     
    Tinkerer likes this.