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Take me to school.......

Discussion in 'Dozers' started by Vetech63, Jun 12, 2018.

  1. Vetech63

    Vetech63 Senior Member

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    Oklahoma
    A customer has contacted me about brakes dragging on a D6T S#WHF00364. I know NOTHING about these. From the sounds of what they are saying it may be leakage or a flow problem. Works great for a hour or 2 in the morning, then they start dragging the machine down. SO...…..Ive got my thinking cap on and ready to learn.
    No active codes that Im aware of. I wont be seeing this machine for a few days so I have a bit of time to study.
     
  2. DMiller

    DMiller Senior Member

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    Got to looking at specs on these, have they gotten away from Hydrostat and gone back to Power shift for real??
     
  3. kshansen

    kshansen Senior Member

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    Any chance you transposed some letters in that S/N? WHF does not seem to work but WFH does.
     
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  4. MHDim

    MHDim Active Member

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    Occupation:
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    Cluj-Napoca, Romania, Europe
    I would operate the machine until the problem appears, and then I would measure the pressures at the brake control valve (located under the operator's seat), AND at the transmission main relief valve (pressure tap should be available outside, at the upper rear of the transmission case).

    LATER EDIT - the brake control valve is under the seat, but in order to check pressures, normally the seat shouldn't need to come off. On D6R, you have access to the brake pressure taps from the rear of the machine... if you have a long arm :) - I think it should be roughly the same on the D6T.

    Brakes are spring-applied and pressure-released; the brake control valve and the transmission are supplied with oil from the same section of the power train oil pump.

    If there's insufficient pressure only at the brake valve, I would start by taking it off, inspecting and thoroughly cleaning it. If all looks OK and/or the problem still persists, and if you say no error codes are present (meaning electronic control system is OK), then I'm afraid it looks like the final drives (together with the brakes) will need to come off, in order to check for worn brake seals...

    If there's insufficient pressure at the brake valve AND at the transmission main relief valve, I'm not 100% sure but I think I would check the main relief valve itself (inside the transmission control valve, under the rectangular cover at the rear of the case) and/or the respective section of the power train pump. I repeat - not 100% sure, but still easier to check than separating both tracks and removing both final drives (including removing the steering diff. motor, which is a pain in the a*$...)...

    Also, if the machine has a ripper, it's worth suspending it on the blade & ripper, and checking if both brakes are dragging, or only one of them.

    Right now I don't have time to look up / attach procedures & instructions, hope I'll be able to do so later tonight, or tomorrow.
    BTW, there seems to be a typo with your s/n - I'm guessing it should be WFH00364 (rather than WHF00364...) :)
     
    Last edited: Jun 13, 2018
    dblaneyfan and Vetech63 like this.
  5. Vetech63

    Vetech63 Senior Member

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    Yes, you are correct. My bad
     
  6. Vetech63

    Vetech63 Senior Member

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    This is power shift for sure.
     
    DMiller likes this.
  7. Vetech63

    Vetech63 Senior Member

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  8. Vetech63

    Vetech63 Senior Member

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    I should have more coffee before I start clicking stuff on here.o_O You have explained it pretty well to me. I don't believe the pressure taps are marked so Im not sure which is which. What kind of brake pressure should I be seeing at operating temp? Is there not a sensor monitored by the computers to measure brake pressure? I would think if its below spec something electrically would be popping up on the display.
     
  9. MHDim

    MHDim Active Member

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    Occupation:
    Service Engineer
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    Cluj-Napoca, Romania, Europe
    I've been extremely busy lately, so I haven't checked in here for a couple of weeks. Sorry about that.
    Did you get the info elsewhere / visit the machine? I had time to have a VERY brief look in SIS today, and from what I see, things are a bit different on the D6T as compared to the D6R's which I'm more familiar with. Not by much, but they have re-located some pressure taps, and the service brakes seem to be operated by a single solenoid valve, rather than separate valves for each track (which was unnecessary anyway IMHO on D6R, since having diff. steering you never have to brake just ONE track).

    Anyway, do you still need info? As far as I know there is NO sensor feeding the ECM with info for brake pressure. If you still have problems, we can search further.
     
  10. Vetech63

    Vetech63 Senior Member

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    I appreciate your assistance. I did get the schematics I needed and traced the problem to a bad brake valve component. Its been repaired and running great! Thank You again!
     
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  11. old-iron-habit

    old-iron-habit Senior Member

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    Thanks for updating all of us with the solution. It is great when we hear the outcome so it can help someone in the future.
     
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