CDL Air Brakes Endorsement Examination Verified
Questions, Correct Answers, and Detailed
Explanations for Science Students||Already Graded
A+
1. What is the main purpose of an air brake system?
A. To reduce fuel consumption
B. To assist steering control
C. To stop and hold the vehicle safely
D. To increase engine power
Air brakes use compressed air to apply braking force, allowing large vehicles to
stop and remain stationary.
2. What supplies the air to the air brake system?
A. Brake chambers
B. Air tanks
C. Air compressor
D. Slack adjusters
The air compressor pumps air into the system and maintains operating
pressure.
3. Where is the air compressor usually mounted?
A. On the trailer
B. On the engine
C. Inside the cab
D. On the axle
The air compressor is engine-driven, typically mounted on or near the engine.
4. What device removes moisture and oil from compressed air?
A. Foot valve
B. Supply valve
,C. Air dryer
D. Relay valve
The air dryer protects the system from moisture and contamination.
5. What happens when air pressure drops too low?
A. Brakes release
B. Spring brakes apply automatically
C. Engine shuts off
D. Steering locks
Low air pressure causes spring brakes to engage as a safety feature.
6. At approximately what PSI should the low air pressure warning activate?
A. 20 PSI
B. 60 PSI
C. 90 PSI
D. 120 PSI
Federal standards require a warning device to activate around 60 PSI.
7. Which brake is used for parking?
A. Service brake
B. Engine brake
C. Spring brake
D. Trailer brake
Spring brakes are designed to hold the vehicle when parked.
8. What color is the parking brake control valve?
A. Blue
B. Yellow
C. Yellow (diamond-shaped)
D. Red
, The parking brake valve is yellow and diamond-shaped.
9. What color is the trailer air supply control?
A. Yellow
B. Black
C. Red
D. Blue
The red octagonal valve controls air supply to the trailer.
10. Which part converts air pressure into mechanical force?
A. Air tank
B. Foot valve
C. Brake chamber
D. Slack adjuster
Brake chambers use air pressure to move a pushrod.
11. What component adjusts brake shoe clearance?
A. Brake drum
B. Slack adjuster
C. Air dryer
D. Relay valve
Slack adjusters keep brake shoes at the proper distance from the drum.
12. What happens when brakes are applied?
A. Air pressure increases in tanks
B. Air pressure flows to brake chambers
C. Springs compress
D. Exhaust valve closes
Pressing the brake pedal sends air to the brake chambers.
Questions, Correct Answers, and Detailed
Explanations for Science Students||Already Graded
A+
1. What is the main purpose of an air brake system?
A. To reduce fuel consumption
B. To assist steering control
C. To stop and hold the vehicle safely
D. To increase engine power
Air brakes use compressed air to apply braking force, allowing large vehicles to
stop and remain stationary.
2. What supplies the air to the air brake system?
A. Brake chambers
B. Air tanks
C. Air compressor
D. Slack adjusters
The air compressor pumps air into the system and maintains operating
pressure.
3. Where is the air compressor usually mounted?
A. On the trailer
B. On the engine
C. Inside the cab
D. On the axle
The air compressor is engine-driven, typically mounted on or near the engine.
4. What device removes moisture and oil from compressed air?
A. Foot valve
B. Supply valve
,C. Air dryer
D. Relay valve
The air dryer protects the system from moisture and contamination.
5. What happens when air pressure drops too low?
A. Brakes release
B. Spring brakes apply automatically
C. Engine shuts off
D. Steering locks
Low air pressure causes spring brakes to engage as a safety feature.
6. At approximately what PSI should the low air pressure warning activate?
A. 20 PSI
B. 60 PSI
C. 90 PSI
D. 120 PSI
Federal standards require a warning device to activate around 60 PSI.
7. Which brake is used for parking?
A. Service brake
B. Engine brake
C. Spring brake
D. Trailer brake
Spring brakes are designed to hold the vehicle when parked.
8. What color is the parking brake control valve?
A. Blue
B. Yellow
C. Yellow (diamond-shaped)
D. Red
, The parking brake valve is yellow and diamond-shaped.
9. What color is the trailer air supply control?
A. Yellow
B. Black
C. Red
D. Blue
The red octagonal valve controls air supply to the trailer.
10. Which part converts air pressure into mechanical force?
A. Air tank
B. Foot valve
C. Brake chamber
D. Slack adjuster
Brake chambers use air pressure to move a pushrod.
11. What component adjusts brake shoe clearance?
A. Brake drum
B. Slack adjuster
C. Air dryer
D. Relay valve
Slack adjusters keep brake shoes at the proper distance from the drum.
12. What happens when brakes are applied?
A. Air pressure increases in tanks
B. Air pressure flows to brake chambers
C. Springs compress
D. Exhaust valve closes
Pressing the brake pedal sends air to the brake chambers.
