CDL Class B - Air Brakes Questions and Answers Graded A+

CDL Class B - Air Brakes Questions and Answers Graded A+ Air brakes use ____ to make the brakes work. Compressed air The ____ brake system applies and releases the brakes when you use the brake pedal during normal driving. Service The _____ brake system applies and releases the parking brakes when you use the parking brake control. Parking The ______ brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure. Emergency What does the air compressor do? The air compressor pumps air into the storage tanks (reservoirs) The air compressor is connected to the engine through ________. Gears or a v-belt There are different kinds of air compressors. How may the air compressor be cooled? -Air cooled -Engine cooling system If the compressor has its own oil supply, what must you be sure to do? Check the oil level before driving What does the air compressor governor do? The governor controls when the air compressor will pump air into the air storage tanks. What do the air storage tanks do? Used to hold compressed air When air tank pressure rises to the "cut-out" level, the governor stops the compressor from pumping air. What level is the "cut-out" level? Around 125 pounds per square inch (psi) When the tank pressure falls to the "cut-in" pressure, the governor allows the compressor to start pumping again. What is the "cut-in" level? Around 100 pounds per square in (psi) True or false? The number and size of air tanks varies among vehicles. The tanks will hold enough air to allow the brakes to be used several times even if the compressor stops working. True Compressed air usually has some water and some compressor oil in it which is bad for the air brake system. Why is it bad for the air brake system? The water can freeze in cold weather and cause break failure What does the alcohol evaporator do? Puts alcohol into the air system to help reduce the risk of ice in air brake valves and other parts during cold weather. If the safety valve releases air, what should you do? Have the fault fixed by a mechanic True or false? To stop, the brake shoes and linings are pushed against the inside of the drum. True What is the most common kind of foundation brake? S-cam What do supply pressure gauges do? Tell you how much pressure is in the air tanks What does the application pressure gauge do? Shows how much air pressure you are applying to the brakes Some older vehicles (made before 1975) have a front brake limiting valve and a control in the cab. The control is usually marked "normal" and "slippery". Which position should the control be in if you are driving an older vehicle with this option? Normal Tractor and straight truck spring brakes will come