CDL Air Brakes (Section 5) Questions and Answers 100% Pass

CDL Air Brakes (Section 5) Questions and Answers 100% Pass What makes air brakes work? Compressed air. What are the three braking systems? Service brake, parking brake, emergency brake What does the service brake do? Applies and releases the brakes when you use the brake pedal during normal driving. What does the parking brake do? Applies and releases the parking brake when you use the parking brake control What does the emergency brake do? Uses parts of the service and parking brake system to stop the vehicle in event of a brake system failure. What does the air compressor do? Pumps air into the air storage tank reservoirs. Connected to the engine through gears or a belt. May be cooled by air or engine cooling system. May have its own oil supply or use engine oil. What does the air compressor governor do? Controls when the air compressor will pump air into the air storage tanks. When it rises to "cut-out" of 125psi it stops the compressor. When it falls to "cut-in" at 100psi it allows it start again. What do the air storage tanks do? Used to hold compressed air. What are the air tank drains? Used to drain water and oil. Can be manaul or automatic. What does the alcohol evaporator do? Puts alcohol into the air system to reduce the risk of ice in air brake valves. Check the container and fill up every day. Daily tank drainage is still necessary. What does the safety valve do? Installed in the first tank and protects the tank and rest of system from too much pressure. Set to open at 150psi. What does the brake pedal do? Pushing harder applies more air pressure. Letting up releases air pressure and releases the brakes. This lets some compressed air out of the tanks. This must be made up by the air compressor. Pressing and holding unnecessarily can let air out faster than it can be replaced. What are foundation brakes? Used at each wheel. Most common type is teh s-cam drum brake. What do brake drums, shoes, and linings go? Drums are located on each end of the axles. The wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes and linings are pushed against the inside of the drum. This causes heat which can be a problem. What are s-cam brakes? When braking air pressure pushes the rod out, moving the slack adjuster, and twisting the brake cam shaft. This turns the s-cam which forces the brake shoes away from one another and against the drum. What are wedge brakes? The brake chamber push rod pushes a wedge directly between the ends of two brake shoes to force them against the drum. May have one or two chambers. What are disc brakes? Instead of an s-cam a power screw is used. What do supply pressure gauges do? Tell how much air pressure is in the tanks. If a dual system there will be one for each half of the system. What does the application pressure gauge