Air Brake Valve

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ncaaref, Jun 14, 2021.

  1. ncaaref

    ncaaref Bobtail Member

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    Nov 7, 2020
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    Hey all, I have a 1994 Ford Areomax L9000. I My MV3 valve is leaking air. I bought a new one and once I got it installed, I push the Tractor brake valve in, then when I push the trailer brake valve in the tractor brake valve pops out. I have it connected the same as the old valve. any help would be greatly appreciated.
     
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  3. Goodysnap

    Goodysnap Road Train Member

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    Jul 12, 2017
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    Im guessing it didnt do that before replacing the valve? Air both primary and secondary systems fully charged when this occurs? What pressure? Do you actually have a trailer connected? Have you tried blocking off the red gladhand on the truck with the same result?


    When all else fails- Bendix is very helpful.

    1800AIRBRAKE
     
  4. ncaaref

    ncaaref Bobtail Member

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    Nov 7, 2020
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    No It did not do it with the old valve. the secondary air supply port had a plug in it on the old valve and so I did the same thing to the new valve. I ended up putting the old valve back in so I could use the truck. This happened when i did not have the trailer connected. I keep caps on both glad hands when i dont have the trailer hooked up.
     
  5. Goodysnap

    Goodysnap Road Train Member

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    Jul 12, 2017
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    Why are you pushing the trailer release valve in with no trailer connected?
    Does the tractor stay charged and brakes released with yellow in?
    Why did you have to put the old valve on to use the truck?
     
  6. ncaaref

    ncaaref Bobtail Member

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    Nov 7, 2020
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    Well I believe the way the air lines are plumbed the trailer line supplies a valve near the back of the truck and it supplies air to the rear axle also. yes when i push the yellow in it releases the tractor brakes, however on the new valve once i push the red button in the tractor valve pops out. that is why i put the old valve back in
     
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