CDL Air Brakes Test 4 – Classic Mode

This is CDL Air Brakes Test 4 in our original Classic Mode. Simply click in your answer to each CDL practice test question. When you're finished, check your score and results. You can reset the test and retake it as needed.


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1. Air loss in a straight truck or bus should not be more than ____ with the engine off and the brakes released.

A 1 psi in 30 seconds
B 1 psi in one minute
C 2 psi in one minute
D 3 psi in one minute

2. To make an emergency stop with air brakes, using the stab braking method, you should:

A Pump the brake pedal rapidly and lightly.
B Brake hard until the wheels lock, and then get off the brakes for as much time as the wheels were locked
C Brake as hard as you can, get off the brakes when the wheels lock, get back on the brakes when the wheels start rolling again.
D Press hard on the brake pedal and apply full hand valve until you stop.

3. You should know that your brakes are fading when:

A Pressure on the brake pedal is released and speed increases.
B You have to push harder on the brake pedal to control your speed on a downgrade.
C The brake feels spongy when pressure is applied
D Less pressure is needed on the brake pedal for each stop

4. To check the free play of manual slack adjusters on s-cam brakes you should:

A Park on level ground, chock the wheels, and release the parking brakes.
B Stop on level ground and apply the parking brakes.
C Park on level ground and drain off air pressure before adjusting.
D Park on a slight grade, release the parking brake, apply the service brakes, and check for vehicle movement.

5. If the air compressor should develop a leak, what keeps the air in the tanks?

A The tractor protection valve
B The emergency relay valve
C The one way check valve
D The air compressor

6. When driving down a long steep hill you should:

A Use stab braking.
B Begin braking when you are 10 M.P.H. above your safe speed.
C Release the brake when you are 5 M.P.H. below your safe speed.
D Use the trailer brakes.

7. The brake system that applies and releases the brakes when the driver uses the brake pedal is the:

A Service brake system.
B Emergency brake system.
C Parking brake system.
D None of the above.

8. The most common type of foundation brakes found on heavy vehicles is the:

A Disc brakes
B Wedge drum
C S-cam drum
D None of the above

9. Vehicles with air brakes must have:

A At least two air tanks.
B An air pressure gauge to show the pressure available for braking.
C An air pressure gauge, to show air used by the brake chambers for braking.
D None of the above.

10. The driver must be able to see a warning that is given before air pressure in the service air tanks falls below:

A 80 psi
B 40 psi
C 20 psi
D 60 psi

End of Test #4

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