How to Replace a Brake Chamber on a Semi Trailer

Written by paisley parmer
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Many issues can arise indicating that the brake chamber of a semi-trailer needs replacement, including air leaks. Replacing the brake chambers can prove to be a difficult task, requiring the person attempting the job to have a sufficient amount of education and experience relating to the brake systems of heavy-duty equipment.

Skill level:
Easy

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Things you need

  • Wheel chocks
  • Standard ¾-inch wrench
  • 12-inch crescent wrench
  • 15/16-inch wrench or ratchet with socket
  • Vice
  • Standard tape measure
  • Soapstone
  • Hacksaw or other comparable cutting device
  • File
  • Needle nose pliers

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Instructions

  1. 1

    Park the tractor on a level surface.

  2. 2

    Apply the emergency parking brakes if the trailer is still hooked up to a semi or check to make sure the emergency parking brakes are applied for a trailer not hooked up to a semi.

  3. 3

    Put wheel chocks under a set of the trailer's wheels.

  4. 4

    Position yourself under the trailer beneath the brake chamber you are working on.

  5. 5

    Remove the chamber caging tool from the side of the brake chamber using a standard ¾-inch wrench.

  6. 6

    Remove the plug from the back of the brake chamber.

  1. 1

    Place the caging tool into the back of the brake chamber, pushing it in as far as it will go.

  2. 2

    Turn the caging tool clockwise until it locks into a groove.

  3. 3

    Try to pull the caging tool out; if it does not move, it is inserted properly.

  4. 4

    Place the nut of the caging tool onto the caging tool; there will be tension. Tighten it all the way down until it stops using a ¾-inch wrench.

  5. 5

    Pull the cottar pins out of the clevis pins (at the end of the brake chamber rod) on the clevis, releasing the slack adjuster.

  6. 6

    Remove the emergency and service air lines and fittings from the brake chamber using a 12-inch crescent wrench.

  7. 7

    Remove the two mounting nuts from the brake chamber that connect them to the chamber bracket on the axle using a 15/16-inch wrench or ratchet with socket.

  8. 8

    Place the chamber into a vice on a hard, level surface.

  1. 1

    Remove the nut from the caging tool using a ¾-inch wrench, allowing for the full extension of the chamber rod.

  2. 2

    Place channel locks onto the clevis of the chamber rod and hold firmly.

  3. 3

    Release the jam nut from the chamber rod using a 15/16-inch wrench.

  4. 4

    Remove the clevis from the chamber rod.

  5. 5

    Measure the chamber rod from the base of the brake chamber to the end of the rod using a standard tape measure then record the measurement for later use.

  6. 6

    Remove the old brake chamber from the vice.

  7. 7

    Discard the old brake chamber.

  1. 1

    Place the new brake chamber into a vice on a level surface.

  2. 2

    Remove the caging tool from the back of the chamber using a ¾-inch wrench.

  3. 3

    Allow the chamber rod to extend fully once the caging tool has been removed.

  1. 1

    Measure from the base of the chamber until you reach the recorded measurement of length for the old chamber and mark the rod at the appropriate location using soapstone.

  2. 2

    Thread the chamber rod nut onto the rod, going past the mark made with the soapstone so that the mark is right behind the nut.

  3. 3

    Cut the rod at the mark made by the soapstone using a hacksaw or other comparable cutting device.

  4. 4

    File any burrs of off the end of the rod.

  5. 5

    Thread the clevis onto the rod of the chamber until the rod is visible on the opposite end of the clevis.

  1. 1

    Position yourself under the trailer again, taking the new chamber with you.

  2. 2

    Place the caging tool into the back of the brake chamber, pushing it in as far as it will go.

  3. 3

    Turn the caging tool clockwise until it locks into a groove.

  4. 4

    Try to pull the caging tool out; if it does not move, it is inserted properly.

  5. 5

    Place the nut of the caging tool onto the caging tool; there will be tension. Tighten it all the way down until it stops using a ¾-inch wrench.

  1. 1

    Place the brake chamber into position, aligning the mounting studs with the holes in the chamber mounting bracket.

  2. 2

    Tighten the mounting nuts onto the chamber's mounting stud, connecting it to the mounting bracket with the 15/16-wrench or ratchet and socket.

  3. 3

    Connect the brake chamber emergency and service air lines using a 12-inch crescent wrench.

  4. 4

    Place the clevis pins into the clevis through the slack adjuster.

  5. 5

    Put the cottar pins into the clevis pins using needle nose pliers.

  6. 6

    Adjust the brake according to manufacture's specifications using a wrench or socket on the slack adjuster.

  1. 1

    Remove the nut from the brake chamber cage tool using a ¾-inch wrench.

  2. 2

    Turn the cage tool counterclockwise until it can be pulled out.

  3. 3

    Remove the cage tool from the back of the brake chamber by pulling it.

  4. 4

    Slide the cage tool into the groove on the side of the brake chamber.

  5. 5

    Lock the cage tool down in place by tightening the nut with a ¾-inch wrench.

  6. 6

    Inspect the brake chamber, with brakes applied, to determine that the angle between the chamber and slack adjuster should be 90 degrees.

  7. 7

    Adjust the clevis by removing the cottar pins from the clevis pins, at the end of the brake chamber rod, from the clevis, releasing the slack adjuster. Adjust accordingly if the angle is more or less than 90 degrees.

  8. 8

    Tighten the chamber rod jam nut against the clevis using a 15/16-inch wrench.

  9. 9

    Remove the wheel chocks from under the tires.

Tips and warnings

  • Measure twice, while initially preparing the chamber rod, to ensure you obtain the proper length and do not render the part useless.
  • Take a mental note of how much of the chamber rod is visible through the clevis, before completing Step four of preparing the chamber rod for disposal, to insure that you properly reinstall the clevis during Step 5 of preparing the new chamber rod.
  • Applying an anti-seizing lubricant to the clevis pins may help assist in replacing the brake chamber.
  • Do not attempt to take the brake chamber apart unless you are a trained professional. When a brake chamber is improperly disassembled, serious injury or death can occur.

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