brake air leak (1993 International 9400-Series 60)

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by RWCDL, Jul 26, 2021.

  1. RWCDL

    RWCDL Bobtail Member

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    Jul 26, 2021
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    When I step on my brake pedal, I get a rapid air leak the harder I press the pedal. I located the air hiss, and it’s coming from outside under the hood coming out of the firewall. It is a small plastic tube that goes no where. I thought either it was a broken tube, but I don’t see where it could go to. Or I thought it could be some sort of breather tube. But that don’t make sense to me either. I know I shouldn’t be losing air from it when I’m pressing the brake. If I can figure out how to upload a picture of it, maybe someone can tell me why it’s leaking brake air. I assume it would not be wise to plug it. Even though it does not leak anymore if I plug it. But I don’t know if that will affect any other part of my air system or braking. Any ideas?
     
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  3. MLC Adventures

    MLC Adventures Medium Load Member

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    Leaks only when brakes are released? Most likely a brake chamber
     
  4. BoxCarKidd

    BoxCarKidd Road Train Member

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    Valves, air wiper motors and such are often vented to outside the cab.
    You should be able to flip a few dash panels out and trace it down. Does it go to the hand valve? Could be a bad tractor protection valve back feeding through the hand valve.
     
    spsauerland Thanks this.
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