Peterbilt Brake Valve Replacement/Leak

Discussion in 'Peterbilt Forum' started by grainhauler, Mar 16, 2012.

  1. grainhauler

    grainhauler Bobtail Member

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    Apr 28, 2007
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    Have a 379 Pete short hood. When I step and hold the brake it leaks down air quickly 10-20psi in 3min. How do you replace the valve under the brake peddle. Sounds like thats where its leaking out off. Doesnt leak if you dont step on the brake.
     
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  3. truckmechanic

    truckmechanic Medium Load Member

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    Jan 14, 2012
    Hi Desert Ca
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    Pain in the a@@ best way is to un hook all Lines that go to front of valve then pull floor panel around shift boot un bolt foot valve and clamp atone hoses and swing whole assy into cab there a pain that's the way I do them you can do it all from outside but this way more room and you can put the valve up and start the bolts by your self also make sure you don't have a relay valve or brake can bleeding through before you take on the foot valve
     
    EverLuc Thanks this.
  4. grainhauler

    grainhauler Bobtail Member

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    Apr 28, 2007
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    Sounds like its coming from the bottom of the cab and not any brake cans. Where would the relay valve be? Pretty new to semis.
     
  5. truckmechanic

    truckmechanic Medium Load Member

    534
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    Jan 14, 2012
    Hi Desert Ca
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    I mean make sure the relay valves and brake cans are not leaking back through to the foot valve you can find the relay valves on the 2nd and 3 rd axle by following. The hoses from the brake cans to the relay valve
     
  6. grainhauler

    grainhauler Bobtail Member

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    Apr 28, 2007
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    How do you check the relay valve? Pulled the panel up around the shifter, can feel air leaking out of the valve bottom.
     
  7. ratchetmanejc4eva

    ratchetmanejc4eva Bobtail Member

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    Oct 18, 2014
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    What was the out come on the brake valve leaking when u changed the valve did it fix the problem im having the same issue on my 379 short hood been going on like three months just noticed tonight when it happened my brake lights stayed on even when I was off the pedal so I taped it and they released and started building air again.
     
  8. ratchetmanejc4eva

    ratchetmanejc4eva Bobtail Member

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    Oct 18, 2014
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    Where are u from grain hauler? I live in Nebraska been wanting to get into hauling grain
     
  9. beltrans

    beltrans Medium Load Member

    441
    101
    Nov 26, 2008
    spokane wa
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    It could be a sticky brake light switch..
     
  10. ratchetmanejc4eva

    ratchetmanejc4eva Bobtail Member

    4
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    Oct 18, 2014
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    Has to b the pedal cause the brake application guage doesn't go all the way back down and I can feel resistance. Then if I tap the brake it will release
     
  11. RobNj379

    RobNj379 Bobtail Member

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    May 23, 2016
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    I have absolutely no pressure in my pedal. I do have it in gauges and trolley. Truck is 2000 379. I'm assuming it's the foot valve.
     
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