Page 1 of 84
CDL Air Brakes EXAM AND PRACTICE TEST ALL 400
Questions and Verified Solutions Latest Update
This Year
QUESTION: What is the name of the device that pumps air into the air storage tanks?
A. Governor
B. Evaporator
C. Safety valve
D. Air compressor - ANSWER-Air compressor. The air compressor pumps air into the air storage
tanks/reservoirs. The governor controls when the air compressor will pump air into the air
storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of
ice in cold weather. A safety valve protects the tank and system from too much pressure.
QUESTION: What is the alcohol evaporator's primary purpose?
A. Remove water and oil from the air brake system
B. Remove alcohol from the air brake system
C. Put alcohol into the air system
D. To heat the air tank - ANSWER-Put alcohol into the air system. An alcohol evaporator puts
alcohol into the air system to help reduce the risk of ice in cold weather.
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QUESTION: What psi level is the safety relief valve set to open at?
A. 150 psi
B. 125 psi
C. 60 psi
D. 100 psi - ANSWER-150 psi. A safety relief valve is installed in the first tank that the air
compressor pumps air into. A safety valve protects the tank and system from too much
pressure by opening up at 150 psi.
QUESTION: Which of the following is the most common type of foundation brake?
A. Wedge brake
B. S-cam drum brake
C. Disc brake
D. Anti-lock brake - ANSWER-S-cam drum brake. Wedge brakes and disc brakes are foundation
brake types that are much less common than S-cam drum brakes. Anti-lock brakes are an add-
on component to an air brake system to help reduce lockup.
QUESTION: Which of the following statements is true regarding front wheel braking?
A. Front wheel braking is good under all conditions
B. Front wheel braking will cause skids on ice
C. You should put a front brake limiting valve (if equipped) on the slippery position in adverse
conditions
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D. Front wheel braking is ineffective in slippery conditions - ANSWER-Front wheel braking is
good under all conditions. Testing has confirmed that front wheel braking will not cause skids,
even on ice. If your vehicle is made before 1975, it may be equipped with a front brake limiting
valve. You should set the valve in the "normal" position, regardless of driving conditions.
QUESTION: At what air pressure must the low air pressure warning signal come on?
A. 150 psi
B. 50 psi
C. 45 psi
D. 60 psi - ANSWER-60 psi. The warning light (or buzzer) must come on when the pressure falls
below 60 psi.
Q: What type of air do air brakes use?
A. Decompressed air
B. Warm air
C. Compressed air
D. Heated air - ANSWER-Compressed air. Air brakes use compressed air for operation and are a
safe way to stop large and heavy vehicles if maintained properly.
QUESTION: What are the three types of brake systems used in a commercial vehicle air brake
system?
A. Hand brake, parking brake, emergency brake
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B. Service brake, parking brake, emergency brake
C. Anti-lock brake, service brake, emergency brake
D. Service brake, hand brake, emergency brake - ANSWER-Service brake, parking brake,
emergency brake. Anti-lock brakes are installed on many vehicles, but are an add-on
component to the air brake system. Some brakes have hand controls, but this is not the name
of one of the components of the air brake systems.
QUESTION: Which of the following statements regarding spring brakes is true?
A. Spring brakes will come on at 60 psi
B. Spring brakes are held by mechanical force
C. Spring brakes use air pressure to stop a vehicle
D. Spring brakes will not function if the system loses air pressure - ANSWER-Spring brakes are
held by mechanical force. Spring brakes use mechanical force to stop a vehicle and are designed
to work if the air pressure becomes too low (under 45 psi).
QUESTION: Which of the following devices indicates how much pressure you have in your air
tanks?
A. Application pressure gauge
B. Low air pressure warning signal
C. Ammeter
CDL Air Brakes EXAM AND PRACTICE TEST ALL 400
Questions and Verified Solutions Latest Update
This Year
QUESTION: What is the name of the device that pumps air into the air storage tanks?
A. Governor
B. Evaporator
C. Safety valve
D. Air compressor - ANSWER-Air compressor. The air compressor pumps air into the air storage
tanks/reservoirs. The governor controls when the air compressor will pump air into the air
storage tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of
ice in cold weather. A safety valve protects the tank and system from too much pressure.
QUESTION: What is the alcohol evaporator's primary purpose?
A. Remove water and oil from the air brake system
B. Remove alcohol from the air brake system
C. Put alcohol into the air system
D. To heat the air tank - ANSWER-Put alcohol into the air system. An alcohol evaporator puts
alcohol into the air system to help reduce the risk of ice in cold weather.
, Page 2 of 84
QUESTION: What psi level is the safety relief valve set to open at?
A. 150 psi
B. 125 psi
C. 60 psi
D. 100 psi - ANSWER-150 psi. A safety relief valve is installed in the first tank that the air
compressor pumps air into. A safety valve protects the tank and system from too much
pressure by opening up at 150 psi.
QUESTION: Which of the following is the most common type of foundation brake?
A. Wedge brake
B. S-cam drum brake
C. Disc brake
D. Anti-lock brake - ANSWER-S-cam drum brake. Wedge brakes and disc brakes are foundation
brake types that are much less common than S-cam drum brakes. Anti-lock brakes are an add-
on component to an air brake system to help reduce lockup.
QUESTION: Which of the following statements is true regarding front wheel braking?
A. Front wheel braking is good under all conditions
B. Front wheel braking will cause skids on ice
C. You should put a front brake limiting valve (if equipped) on the slippery position in adverse
conditions
, Page 3 of 84
D. Front wheel braking is ineffective in slippery conditions - ANSWER-Front wheel braking is
good under all conditions. Testing has confirmed that front wheel braking will not cause skids,
even on ice. If your vehicle is made before 1975, it may be equipped with a front brake limiting
valve. You should set the valve in the "normal" position, regardless of driving conditions.
QUESTION: At what air pressure must the low air pressure warning signal come on?
A. 150 psi
B. 50 psi
C. 45 psi
D. 60 psi - ANSWER-60 psi. The warning light (or buzzer) must come on when the pressure falls
below 60 psi.
Q: What type of air do air brakes use?
A. Decompressed air
B. Warm air
C. Compressed air
D. Heated air - ANSWER-Compressed air. Air brakes use compressed air for operation and are a
safe way to stop large and heavy vehicles if maintained properly.
QUESTION: What are the three types of brake systems used in a commercial vehicle air brake
system?
A. Hand brake, parking brake, emergency brake
, Page 4 of 84
B. Service brake, parking brake, emergency brake
C. Anti-lock brake, service brake, emergency brake
D. Service brake, hand brake, emergency brake - ANSWER-Service brake, parking brake,
emergency brake. Anti-lock brakes are installed on many vehicles, but are an add-on
component to the air brake system. Some brakes have hand controls, but this is not the name
of one of the components of the air brake systems.
QUESTION: Which of the following statements regarding spring brakes is true?
A. Spring brakes will come on at 60 psi
B. Spring brakes are held by mechanical force
C. Spring brakes use air pressure to stop a vehicle
D. Spring brakes will not function if the system loses air pressure - ANSWER-Spring brakes are
held by mechanical force. Spring brakes use mechanical force to stop a vehicle and are designed
to work if the air pressure becomes too low (under 45 psi).
QUESTION: Which of the following devices indicates how much pressure you have in your air
tanks?
A. Application pressure gauge
B. Low air pressure warning signal
C. Ammeter
