6420 hydraulics hissing-load sence
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Thread: 6420 hydraulics hissing-load sence

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    6420 hydraulics hissing-load sence

    I have 3 20 series john deeres (6320, 6420, 7320) and they all do it. The pump load senses because of a broken o-ring in the back of the brake valve. I have replaced every one ( just the broken o-rings) and its almost an annual job on each tractor, o ring keeps going bad, the 20's were known for this. My question is there any update to remedy this? It looks like on JD parts there are no superseeding part numbers on the o ring or the little plunger/check valve the o ring goes on. Just wondering of anyone out there has heard/seen this and has found a solution? the 2 6000's don't overheat the hydraulic oil but the 7320 gets pretty hot from the pump always being pressured from the internal leak causing the pump to be in stroke.

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    Zebrafive's Avatar
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    Which o-ring?, see drawing. Have you tried different o-ring material? Viton or Silicone?
    Attached Thumbnails Attached Thumbnails 6415brakevalve.PNG  
    J
    John Deere 2030 w/245SL Loader
    John Deere 6415 w/640SL Loader
    John Deere 285 50" deck Stolen May 2017
    John Deere x485 62" deck AWS
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    The o-ring is not on your picture, nor is the check valve. the o-ring part # is L164885 and the check valve that the o ring fits on the end of is AL113726. Not sure if there any remedy's. Also the oring is very specific and cant be duplicated in a metric oring kit from what i remember, otherwise id certainly try another type, but I feel its not a quality issue, more a design issue.

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    Zebrafive's Avatar
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    OK, I found it. Brake valve with front wheel brakes. The O ring is key 11.
    Specs are 10mm ID 12.8mm OD 1.4mm diameter stock, material PTFE

    L164885 replaced L53976 which was 10mm ID 13mm OD 1.5mm diameter stock, material Nitrile

    Maybe go back to the old P/N?
    Attached Thumbnails Attached Thumbnails 6420brakevalve11.PNG   6420brakecheckvalve.PNG  
    Last edited by Zebrafive; 05-22-2019 at 09:31 PM.
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    John Deere 2030 w/245SL Loader
    John Deere 6415 w/640SL Loader
    John Deere 285 50" deck Stolen May 2017
    John Deere x485 62" deck AWS
    Kawasaki Mule 2510 4x4 bought new 1996
    Ford F250 4x4 bought new 1978

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    I have the same problem with my 6420 as you are describing. A hissing sound coming from the hyd pump area. Can you please explain where the faulty o-ring is at so I can check mine. For some reason I cannot view the attachments previously posted. Thanks

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    Basically the o-ring is in the upper back part of the brake valve if your sitting in the seat. brake Valve must be removed from tractor, 3 or 4 steel lines have to be disconnected on the bottom of valve, electrical plug (valve is easier to remove if the sensor is removed, there is an oil hose with hose clamp behind it that needs to be loosened) and 2 Allen head bolts cross-ways. I forget exactly the fitting to remove on the bottom of the valve but its helpful to remove one to push the valve upward and diagonal out of the valve (also need to remove plug #7 on top of brake valve). there is a check valve with an o-ring on the very end of the valve and it is usually broken and chewed up. As for a permanent fix im still not sure because it reoccurs every 100-200 hours for me.

    here is a link to the page of the brake valve, hope it works.

    John Deere Parts Catalog

    valve is AL113726 and o-ring is at the end of it. its also really nice if you have a right hand side door for access, otherwise its tougher like it is on my 7320 standing on my head lol!
    Last edited by bcbrouwer; 06-05-2019 at 08:22 PM.

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    Thanks for the information. I will have to look into this. Like you, my hydraulic oil is not overheating but I have noticed the pump hissing and occasionally when I apply the brakes I hear a squealing sound for a split second coming from the brake valve. However, the brakes have never failed to work so I didn’t consider it an issue.

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