CDL Air Brakes (Section 5) Exam 2025
Questions and Answers
What makes air brakes work? - --CORRECT ANSWER--Compressed air.
What are the three braking systems? - --CORRECT ANSWER--Service brake,
parking brake, emergency brake
What does the service brake do? - --CORRECT ANSWER--Applies and releases
the brakes when you use the brake pedal during normal driving.
What does the parking brake do? - --CORRECT ANSWER--Applies and releases
the parking brake when you use the parking brake control
What does the emergency brake do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
, What does the air compressor governor do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--Used to hold
compressed air.
What are the air tank drains? - --CORRECT ANSWER--Used to drain water and
oil. Can be manaul or automatic.
What does the alcohol evaporator do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
Questions and Answers
What makes air brakes work? - --CORRECT ANSWER--Compressed air.
What are the three braking systems? - --CORRECT ANSWER--Service brake,
parking brake, emergency brake
What does the service brake do? - --CORRECT ANSWER--Applies and releases
the brakes when you use the brake pedal during normal driving.
What does the parking brake do? - --CORRECT ANSWER--Applies and releases
the parking brake when you use the parking brake control
What does the emergency brake do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
, What does the air compressor governor do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--Used to hold
compressed air.
What are the air tank drains? - --CORRECT ANSWER--Used to drain water and
oil. Can be manaul or automatic.
What does the alcohol evaporator do? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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? - --CORRECT ANSWER--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.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
