Random air line leaking when press brakes... Anyone know what this is?

Discussion in 'Kenworth Forum' started by Green461, Sep 13, 2019.

  1. Green461

    Green461 Light Load Member

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    Mar 22, 2019
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    I traced it back and it goes into the center of the firewall above the center of the engine. It inserts into a sleeve, not a push-connect connector, so it isnt meant to be important i'd think. I easily pulled it out, hit the brake and it leaks air there. Then on the inside I took pic, lines either go to the diff lock or the suspension dump switch (i forget which one). Not sure why it leaks when the brake pressed. What is this manifold on the inside, 3rd pic? Could it be bad? or just plug the tube?
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  3. spsauerland

    spsauerland Road Train Member

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    That ain't factory plumbing! Manifold is primary (rear) brake manifold is simply a manifold, nothing to go bad. Somebody has been in there that probably shouldn't have been. Cap it in the cab.
     
    pushbroom Thanks this.
  4. Green461

    Green461 Light Load Member

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    Mar 22, 2019
    Southern WI
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    Inside? The lines go to either the diff lock or suspension dump, they are functional and i'd like to keep. Where is goes through the firewall is just a slide in rubber boot that the tube goes in, if I plugged that i'd imagine id have to hose clamp or pressure would pop it right out.
     
  5. spsauerland

    spsauerland Road Train Member

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    How are they both functional if the 1/4" hose is disconnected?
     
    pushbroom Thanks this.
  6. Green461

    Green461 Light Load Member

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    Mar 22, 2019
    Southern WI
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    I did some more digging this morning, my mistake was I thought the orange 1/4" line labeled #85 going into the firewall would be a 1/4" line coming out and assumed it was one of those in the pic above, it isnt, on the inside it is actually a black 3/8" line and it goes to the left side of the MV3 valve, the trailer brake release side of it. I disconnected the line from the dash and sure enough air comes out when brake pedal is pressed, air also comes out when the trailer brakes are release (press big red button). So not sure whats up?

    The truck is now a flat bed and will never have air trailer brakes again or a use for that red trailer brake release, so that side of the MV3 valve will never be used, if that MV3 valve is bad i wonder if I can just cap this 3/8" black line?

    The black 3/8" line went pretty far through the dash, like a an inch and a half so the push connect it goes into doesnt seem to have a bottom to it, which then comes out the other side and through a rubber boot. Not really a pressure sealed fitting, more of a vent it appears.

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