Air brakes question

Discussion in 'Freightliner Forum' started by Doublebhauling, Jun 18, 2024.

  1. Doublebhauling

    Doublebhauling Bobtail Member

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    Jun 17, 2024
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    I have a 2003 FL 112.
    The brake system has been long overdue for some attention.
    (It's a 10 wheeler manure truck and we're usually not on roads)
    Now getting on to the issue.
    It started as the brakes not wanting to set when the yellow handle was pulled.
    (would usually take about 15 to 20 seconds to set)
    That issue was remedied by tapping on the foot valve and then they would set with a loud psssshh.
    Now they issue is they won't release when the yellow handle on the mv3 valve is pressed in.
    It just leaks out of the abs relay that's bolted to the rear crossmeber.
    I have a new abs relay but I dont quite think that's the issue.
    When I apply shop pressure to the abs air port all of the brakes disengage. Then when I released they set again with a healthy psshhh.
    Thanks for reading this far!
     
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  3. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    May 2, 2021
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    Probably the quick release valve. Pinch off the blue signal line between the quick release valve and the ABS Valve.

    If it quits leaking the quick release valve is bad
     
    Doublebhauling Thanks this.
  4. Doublebhauling

    Doublebhauling Bobtail Member

    7
    1
    Jun 17, 2024
    0
    Thanks for the speedy reply.
    Do you know where I can find the quick release valve?
    Will this fix the issue of the brakes setting slow when the yellow handle is pulled?
    Or should it also fix the leaking air when the yellow handle is applied. Thanks again.
     
  5. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    Very likely could fix both. Both symptoms can be caused by it. Usually mounted on the same crossmember as the ABS valve, on the other side of the crossmember, or on the crossmember in front or vehind.

    Follow the blue 3/8" air line.

    Usually both are under the 5th wheel. So roughly above the middle of the duals
     
    ElmerFudpucker Thanks this.
  6. Doublebhauling

    Doublebhauling Bobtail Member

    7
    1
    Jun 17, 2024
    0
    Ok I will look again tomorrow.
    The only lines I see are the green and black.
    (The blue color appears to be black)
    If I apply shop air to the green side all the brakes release and then go back to normal when I take air away with a loud psshhh.
    I'll keep researching.
     

    Attached Files:

  7. SWM_TECH

    SWM_TECH Light Load Member

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    Apr 15, 2018
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    Could the push rod seal in one of your brake chambers be leaking and allowing air from the parking brake side to back feed out of the service side hoses? You might try supplying air to release the parking brakes and then go around and pinching of the service side hose of each chamber and see if will stop the air feed out of abs valve.
     
  8. Doublebhauling

    Doublebhauling Bobtail Member

    7
    1
    Jun 17, 2024
    0
    Thanks for the suggestions.
    I have capped all of the lines off to the cans 1 at a time.
    It still leaks out the vent
    I have put shop air to each side of the ports on the cans.
    They all articulate back and forth without leaking any air.
    I'm thinking there's something wrong somewhere else.
    I can send air to the abs relay pictured above with shop air and it releases all the brakes as it should.
     
  9. SWM_TECH

    SWM_TECH Light Load Member

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    Apr 15, 2018
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    If you treadle (foot) valve is sticking won't the anti-compounding valve cause the spring brakes to slowly apply so not do damage your brakes. You might want to clean around the treadle valve and disassembly the top and make sure you no longer have any binding.
     
  10. SWM_TECH

    SWM_TECH Light Load Member

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    Apr 15, 2018
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    Perhaps, it more correct to say the anti-compounding feature your brake valve, as a multi-functional spring brake modulating valve will incorporate hold-off regulator, quick-release, anti-compounding and inversion valve features all in one valve. But if treadle valve is sticking and not releasing air sent to the valve you posted picture of it could cause slow application of spring brakes.
     
  11. Doublebhauling

    Doublebhauling Bobtail Member

    7
    1
    Jun 17, 2024
    0
    Thanks for the suggestions! I'm replacing the quick release valve first, the diaphragms inside are all worn out.
    Fingers crossed.
     
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