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When I set my trailer brakes…

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by nikmirbre, Jul 25, 2025 at 6:51 PM.

  1. Jul 25, 2025 at 6:51 PM #1
    nikmirbre

    nikmirbre Road Train Member

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    IMG_2748.jpeg Air leaks from this hole in my firewall, and from the bottom of one of my brake valves under the trailer…. Am I safe to assume that I need to change the brake valves?
    IMG_2745.jpeg
     
    nikmirbre, Jul 25, 2025 at 6:51 PM
    nikmirbre, Jul 25, 2025 at 6:51 PM
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    Rugerfan Thanks this.
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  3. Jul 25, 2025 at 6:51 PM #2
    nikmirbre

    nikmirbre Road Train Member

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    The wetness on the valve is PB Blaster
     
    nikmirbre, Jul 25, 2025 at 6:51 PM
    nikmirbre, Jul 25, 2025 at 6:51 PM
    #2
  4. Jul 25, 2025 at 9:27 PM #3
    JB7

    JB7 Heavy Load Member

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    Are you saying that air leaks then stops or that air continues to leak after the trailer park brake is set?
    Are these the only 5 air lines connected to the valve? Can't tell if either the red or blue line behind the valve are connected to the valve.
    Follow a B line. Probably goes to the spring brake end of a chamber which is not the end closest to the slack adjuster.
    If so, remove line A to make sure that air is not coming out of it.
    upload_2025-7-25_21-13-34.png
     
    JB7, Jul 25, 2025 at 9:27 PM
    JB7, Jul 25, 2025 at 9:27 PM
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    nikmirbre Thanks this.
  5. Jul 25, 2025 at 9:50 PM #4
    kwswan

    kwswan Road Train Member

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    That's the quick release valve for the spring brakes. I had 1 doing the same thing back in the spring.
     
    kwswan, Jul 25, 2025 at 9:50 PM
    kwswan, Jul 25, 2025 at 9:50 PM
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    nikmirbre Thanks this.
  7. Jul 25, 2025 at 9:54 PM #5
    nikmirbre

    nikmirbre Road Train Member

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    High Point NC
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    What did you end up doing?
     
    nikmirbre, Jul 25, 2025 at 9:54 PM
    nikmirbre, Jul 25, 2025 at 9:54 PM
    #5
  8. Jul 25, 2025 at 9:59 PM #6
    nikmirbre

    nikmirbre Road Train Member

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    High Point NC
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    The air leaks from the hole in the center of that valve, and from that hole on the firewall for a good...45 seconds maybe. Id have to get up under my trailer and see if that blue line is actually connected to that valve.

    While its leaking(after I set brakes) if I run under there and plug that hole with my finger, I can hear all the brakes set( scared me the 1st time I done it cause I was laying under there)
     
    nikmirbre, Jul 25, 2025 at 9:59 PM
    nikmirbre, Jul 25, 2025 at 9:59 PM
    #6
  9. Jul 25, 2025 at 10:08 PM #7
    kwswan

    kwswan Road Train Member

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    Put a new one on.
     
    kwswan, Jul 25, 2025 at 10:08 PM
    kwswan, Jul 25, 2025 at 10:08 PM
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    nikmirbre Thanks this.
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