The brake cans for air brakes are better known as air brake chambers. They are responsible for supplying the air needed to turn the brake shoe slack adjuster back and forth. When the air brakes are applied, the brake chambers push the brake chamber rod against the slack adjuster to turn the scam. The scam then compresses the brake shoes to the brake drums. When the air brakes are released, the brake chamber rod pulls the slack adjuster forward to retract the brake shoes away from the brake drums.
Park the truck or trailer onto a flat surface and apply the air brakes. Slide the wheel chocks in the front of the rear wheels and on the back of the rear wheels. Release the air off of the air brakes.
Slide under the truck or trailer and locate the air brake chambers connected near the rear axles. The brake chambers have a threaded rod that retracts out of the rear of the chamber and connects to the slack adjusters.
Measure the distance of the threaded rod from the back of the brake chamber to where the rod connects to the clevis that is attached to the bottom of the slack adjuster with a measuring tape. Write down the measurement on a piece of paper or a notepad with a pen.
Remove the T-tool from the side of one of the brake chambers. If the T-tool is not attached to the side of the brake chamber, you will need to purchase a T-tool for a air brake chamber. Pull the rubber plug out of the front of the brake chamber with your hand. Screw the threaded end of the T-tool into the threaded plate inside of the chamber. Turn the end of the tool clockwise until the tool is secured to the inside of the plate. Screw the nut down on the tool until the nut makes contact with the plate inside of the chamber. Continue to turn the nut clockwise with an adjustable wrench until the nut stops turning. Once the nut stops turning, the brake chamber will be caged and safe to remove.
Loosen and remove the two service air lines from the top of the brake chamber with a open end metric wrench. Loosen and remove the mounting nuts that connect the brake chamber to the mounting bracket with a ratchet and a socket. Straighten and remove the cottar pin that holds the clevis pin inside of the clevis attached to the end of the threaded rod and the slack adjuster with the pliers. Pull the clevis pin out of the clevis with your fingers. Move back to the front of the brake chamber and pull it out of the bracket.
Place the new brake chamber inside of a vice and measure the threaded rod from the backside of the brake chamber until you reach the measurement number that you have written down. Mark the exact location of the measurement on the new rod with a piece of chalk. Cut the rod off straight across the marked measurement with the hacksaw. Once the new rod is cut, it should be the same exact distance as the old rod. File down the rough edges of the new threaded rod with a file.
Slide the brake chamber back through the bracket and reverse the same process as outlined in the steps above to reconnect the brake chamber, air lines and the threaded rod. Make sure that the brake chamber mounting bolts are torqued to 100Ft. Lbs with a torque wrench and a socket.
Crank the truck and release the air brakes. Inspect the new brake chamber to make sure that there are no air leaks and that the new brake chamber is moving the slack adjuster back and forth. Apply the brakes and shut the engine off. Remove the wheel chocks.
Most all air brake chambers come equipped with a caging tool (T-tool) strapped to the side of the brake chamber. If not, you can purchase the caging tool at most any truck and trailer parts stores. Be sure to get an exact measurement when cutting the new threaded rod so that the new brake chamber will fit to the slack adjuster properly.
Be sure to use the wheel chocks behind the wheels to prevent the truck or trailer from rolling while you are under it.