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  1. #1
    New Member
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    John Deere 790

    Default JW-03 Backhoe Problems

    Hey guys,
    I was using my jw03 backhoe today when the boom lift function stopped working. It has been kind of slow in the past and now it has gotten to the point where the boom just sinks down instead of raising up. However after moving around all the other cylinders for a while, the boom will randomly raise back up and then stop working again. Anyone had this problem?
    2007 John Deere 790 with 300 loader, ballast box, and Jinma 3 pt. backhoe.

  2. #2
    Elite Member Bob Rooks's Avatar
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    Bothell & Silverdale, WA
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    Yuchai Bulldozer

    Default Re: JW-03 Backhoe Problems

    I had a LW-6. Same thing happened to me. Cup seals are blown in the boom cylinder. Is your hydraulic oil kinda dark? If so, the seals have disintegrated. The good news is that the cylinder overhaul kits have urethane (opaque white color) seals instead of rubber.
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, Trimble machine control GCR-2SM laser receivers.

  3. #3
    Elite Member RonMar's Avatar
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    Jinma 284 delivered 06/28/05

    Default Re: JW-03 Backhoe Problems

    Quote Originally Posted by cv63usafsfs View Post
    Hey guys,
    I was using my jw03 backhoe today when the boom lift function stopped working. It has been kind of slow in the past and now it has gotten to the point where the boom just sinks down instead of raising up. However after moving around all the other cylinders for a while, the boom will randomly raise back up and then stop working again. Anyone had this problem?
    If you put the boom in a position, does it stay there, or does it sink down by itself? IE, will the boom cylinder support the weight of the boom? If it stays in place, I am going to have to disagree with Bob, and say the seals are probably OK. All the other circuits take a fraction of the hydraulic pressure to move compared to the boom up command. The control valve does not have individual load check valves, so when you give a boom up command, the pressure in the main input gallery must be greater than the pressure created in the cylinder by the weight of the boom. Boom going down when you command up(if that is the only command being given) is a classic symptom of low pressure in the main valve gallery. There is a check valve at the valve inlet, under that large standard screw head on the left side of the valve when seated, directly above the pressure relief valve. This keeps fluid from flowing backward into the pump outlet. So if the fluid cannot go back to the pump, where can it go? All this points to a leaking pressure relief valve IMO.

    You need to hook up a pressure gauge and see what pressure you are getting. If you search back thru this forum, for this type BH, I posted an article about a little adapter I cooked up using a metric to NPT adapter that screws down in place of that screw head cap above the check valve. Into this you can screw in a pressure gauge to easilly test the pressure that the relief valve is delivering to the system when you load up a circuit...
    Last edited by RonMar; 06-14-2011 at 04:07 PM.
    Ron

  4. #4
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    John Deere 790

    Default Re: JW-03 Backhoe Problems

    Thanks for the replies!
    The boom does not sink down until the I give it the boom up command. I am kind of new to tractoring and even newer to this backhoe. It did not come with a manual so I am kind of flying blind as to what the different parts are. Anyone have a labeled picture or something that I could use to figure out what all the parts are and get my bearings straight?
    2007 John Deere 790 with 300 loader, ballast box, and Jinma 3 pt. backhoe.

  5. #5
    Elite Member Bob Rooks's Avatar
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    Yuchai Bulldozer

    Default Re: JW-03 Backhoe Problems

    You probably nailed it Ron. Pump or PRV issues.
    I forgot about the sinking boom, which mine did.
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, Trimble machine control GCR-2SM laser receivers.

  6. #6
    Super Star Member J_J's Avatar
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    JACKSONVILLE, FL
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: JW-03 Backhoe Problems

    You might try removing the load checks and cleaning, or the piston seals in the cyl are bad.

    Check the relief pressure for correct setting.
    Last edited by J_J; 06-15-2011 at 03:23 PM.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  7. #7
    Elite Member RonMar's Avatar
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    Jinma 284 delivered 06/28/05

    Default Re: JW-03 Backhoe Problems

    Quote Originally Posted by J_J View Post
    You might try removing the load checks and cleaning, or the piston seals in the cyl are are bad.

    Check the relief pressure for correct setting.

    Simple valve, no load checks. It only has a single checkvalve at the valve block inlet... You pretty much only ever command boom up by itself on these hoe's. Boom up with any other command = boom going down and the other command happening at an accelerated rate fed by the fluid from the heavily loaded boom cylinder backfeeding the system and providing additional flow to the other lightly loaded circuit.


    cv63usafsfs What type pump are you feeding this BH with from your JD tractor? what engine RPM are you running? I might have a diagram I can upload tonight, I will look when I get home.
    Ron

  8. #8
    Gold Member erj's Avatar
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    Buckley, WA

    Default Re: JW-03 Backhoe Problems

    cv63usafsfs
    Send me a PM with your Email address and I can send you a PDF file of the User Manual which contains part breakdowns.
    RonJ
    2006 Jinma 284, Coldwater FEL, JW03 Backhoe, 5' Box Blade

  9. #9
    Elite Member RonMar's Avatar
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    Jinma 284 delivered 06/28/05

    Default Re: JW-03 Backhoe Problems

    Quote Originally Posted by erj View Post
    cv63usafsfs
    Send me a PM with your Email address and I can send you a PDF file of the User Manual which contains part breakdowns.
    RonJ
    Cool Ron, that was the one I was thinking I have at home, which I got from you
    Ron

  10. #10
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    John Deere 790

    Default Re: JW-03 Backhoe Problems

    ERJ I sent you a PM. I don't know the specific type, just that its a PTO pump and not a power beyond from the JD. I usually run it around 10,000 - 12,000 RPM, slightly above idle. I ran into a marine hydraulics guy today at work and ran the question by him. He thought it might be a lack of pressure which is causing the pressure release valve of the cylinder to not function or a stuck release valve. Thats what I was kind of thinking and would explain why just that one function doesnt work but may randomly work when the fluid is cooler. What do you guys think?
    2007 John Deere 790 with 300 loader, ballast box, and Jinma 3 pt. backhoe.

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