What is causing my air leak?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by motrkman, May 1, 2011.

  1. May 1, 2011 #1
    motrkman

    motrkman Bobtail Member

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    May 1, 2011
    Dixon, MO
    0
    Short background on my problem. I drive a '99 Freightliner FLD 120 and pull an '08 Kentucky trailer. A couple weeks ago, I had to get on the brakes pretty hard. After this, I heard air leaking under the trailer when I applied the service brake. I found the air was coming out of the ABS relay valve exhaust port. So, my mechanic and I replaced the valve. Still leaking air. So we replaced the ETV valve under the trailer. Still leaking air. We hooked a different tractor up to the trailer and applied the service brake. No leak.
    So, something on my tractor is causing the problem. But, I am clueless as to what it might be. Air is only discharged through the ABS relay valve when the service brake is applied. And it does it with both the foot pedal and Johnson bar.
    Any help would be greatly appreciated.
     
    motrkman, May 1, 2011
    motrkman, May 1, 2011
    #1
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  3. May 1, 2011 #2
    Heavyd

    Heavyd Road Train Member

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    Did you hook up both red and blue lines to the trailer with the second truck? Try leaving the trailer cord unhooked with your truck and see if it still does it. Sounds like the exhaust solenoid may be energized all the time, may be an electrical problem with the ABS.
     
    Heavyd, May 1, 2011
    Heavyd, May 1, 2011
    #2
  4. May 1, 2011 #3
    AUSSIE DAVE

    AUSSIE DAVE Road Train Member

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    OZ - Brisbane
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    sorry cant help, but Pablo_AU is pretty dam good with air issues.
     
    AUSSIE DAVE, May 1, 2011
    AUSSIE DAVE, May 1, 2011
    #3
  5. May 1, 2011 #4
    motrkman

    motrkman Bobtail Member

    4
    1
    May 1, 2011
    Dixon, MO
    0
    Heavyd,

    Yes we did disconnect the pigtail, with no effect on the problem. And yes we did hook up both airlines with the other truck.
     
    motrkman, May 1, 2011
    motrkman, May 1, 2011
    #4
  7. May 2, 2011 #5
    dr1c

    dr1c Light Load Member

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    Apr 10, 2011
    Alberta
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    Brake pot bypassing....Try blocking 1 at a time off
     
    dr1c, May 2, 2011
    dr1c, May 2, 2011
    #5
  8. May 2, 2011 #6
    Heavyd

    Heavyd Road Train Member

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    I thought that too right away. That is what normally happens when you are releasing the parking brake, so air would leak all the time. His is only leaking when you are applying service brake.

    BTW, what is an ETV valve?
     
    Heavyd, May 2, 2011
    Heavyd, May 2, 2011
    #6
  9. May 2, 2011 #7
    motrkman

    motrkman Bobtail Member

    4
    1
    May 1, 2011
    Dixon, MO
    0
    Sorry my typo, TEV valve (trailer emergency valve). And, yes we tried clamping off the air lines going to the brake chambers. That did not have any effect on the problem either.
    I appreciate the input. Please keep suggestions coming.
     
    motrkman, May 2, 2011
    motrkman, May 2, 2011
    #7
  10. May 5, 2011 #8
    motrkman

    motrkman Bobtail Member

    4
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    May 1, 2011
    Dixon, MO
    0
    My mechanic figured it out. Problem was caused by a faulty tractor protection valve.
     
    motrkman, May 5, 2011
    motrkman, May 5, 2011
    #8
    mrtrdrvr Thanks this.
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