System Parts
What is the purpose of the air compressor in an air brake system?
- ATo release the parking brakes automatically
- BTo apply the service brakes evenly
- CTo warn the driver of low air pressure
- DTo pump air into the air storage tanksCorrect
Why: The air compressor pumps air into the storage tanks (reservoirs) that hold the compressed air used for braking. It is usually connected to the engine by gears or a belt. Without it, the system could not build or maintain the air pressure the brakes need to work.
Inspection
During a walk-around inspection, how do you check manual slack adjusters on S-cam brakes?
- ABy spinning the wheel by hand
- BBy listening for air leaks at the wheel
- CBy measuring the air pressure at each chamber
- DBy pulling hard on each one and checking that it moves no more than about one inchCorrect
Why: With the parking brakes released and wheels chocked, pull hard on each manual slack adjuster you can reach. If it moves more than about one inch from where the pushrod attaches, it is probably out of adjustment. Brakes that are out of adjustment do not work properly and are unsafe.