Can someone please help me with my trailer air brake problem???

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Supertrucker47, Sep 18, 2018.

  1. AModelCat

    AModelCat Road Train Member

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    Got the lines on the right way? If you reversed the gladhands the trailer brakes will typically stay released until you hit the service brakes, then they'll lock up.
     
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  3. Supertrucker47

    Supertrucker47 Bobtail Member

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    Yeah I switched them to see if it changed anything but it didn't work so hoses are good trailer valve is brand new. Just won't release service brake air. Might try to change tractor protection valve maybe
     
  4. bjrc

    bjrc Light Load Member

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    The truck brakes wont sound much different whether the trailer is hooked up or not. If you can hear the trailer brakes exhausting air upon release of the brake pedal then it seems that it is trying to work. If you could read the apply pressure off of the dash gauge (if you have one) that will tell you if the truck is working properly or tee a pressure gauge into the blue trailer hose. The blue hose only works a relay valve on the trailer and it in turn exhausts the brake servos.
     
  5. AModelCat

    AModelCat Road Train Member

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    Another thought: you said you didn't air up the trailer to pull it home and being that its older I have to ask does it even have spring park brakes?
     
  6. bjrc

    bjrc Light Load Member

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    Might also check trailer brake chambers for broken return springs. Not uncommon for brakes to rust up and stick to drums if has been sitting awhile and not want to release.
     
  7. bjrc

    bjrc Light Load Member

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    Another thing if you do have brake chamber problems don't take the spring brake chambers apart if you don't know how. very dangerous! They must be caged first.
     
  8. Supertrucker47

    Supertrucker47 Bobtail Member

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    Yeah I forgot to mention no parking brakes just single chambers. And I thought about the brakes sticking because it was sitting for a while but the parking brake come on and releases good so it shouldn't be that
     
  9. Supertrucker47

    Supertrucker47 Bobtail Member

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    Yeah thanks. I had to change one of the chambers it was rusted so bad the spring was about to burst through I was nervous taking it off haha
     
  10. AModelCat

    AModelCat Road Train Member

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    Ok those older trailers use what is called a relay-emergency valve:
    https://www.wabco-auto.com/wabcoindiaproducts/conventional-products/valves/relay-emergency-valve/

    It actually charges the trailer tanks, "dynamites" the service brakes and functions as a trailer brake relay valve.

    When you charge the trailer from empty the service brakes should dynamite right away, then release again once you get over a certain air pressure.

    Also important to note that this trailer has NO park brakes. Once reservoir pressure drains out, the brakes will gradually release.
     
  11. AModelCat

    AModelCat Road Train Member

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    I also see that you mentioned you had to break the service gladhand to release the trailer brakes. That is not normal. Once you release the brake pedal or trailer spike that line should exhaust. I'd check your exhaust ports on the valves in the trailer service circuit on the truck.
     
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