CDL Air Brake - Commercial Driver's License Air Brakes Pre-Trip Air Brake Inspection Questions and Answers

Question 1

During a static air leakage test on a combination vehicle, what is the maximum permissible pressure drop in one minute after the initial drop?

Accepted Answer

3 psi

Answer

2 psi

Answer

4 psi

Answer

5 psi

Question 2

A driver is performing a pre-trip inspection and tests the low air pressure warning device. At what pressure should the warning light and buzzer typically activate?

Accepted Answer

At or above 60 psi

Answer

Below 80 psi

Answer

At or above 100 psi

Answer

Between 20 and 40 psi

Question 3

When testing the air compressor governor, what are the typical cut-in and cut-out pressures?

Accepted Answer

Cut-in at 100 psi, cut-out at 125 psi

Answer

Cut-in at 80 psi, cut-out at 110 psi

Answer

Cut-in at 125 psi, cut-out at 150 psi

Answer

Cut-in at 60 psi, cut-out at 90 psi

Question 4

A driver applies and holds the foot brake for one minute with the engine off. For a single vehicle, what is the maximum allowable air pressure loss during this applied leakage test?

Accepted Answer

3 psi

Answer

4 psi

Answer

2 psi

Answer

5 psi

Question 5

Which of the following steps is performed to test that the spring brakes will engage automatically?

Accepted Answer

Pump the brake pedal to reduce air pressure until the parking brake valve pops out.

Answer

Gently pull against the parking brake in a low gear.

Answer

Build the air pressure to the governor cut-out.

Answer

Apply the service brake firmly while moving at 5 mph.

Question 6

What is the primary purpose of the tractor protection valve, which is checked during a pre-trip inspection?

Accepted Answer

To prevent total air loss from the tractor if the trailer breaks away or has a major leak.

Answer

To prevent the trailer brakes from locking up during hard braking.

Answer

To regulate the air pressure sent to the service brakes.

Answer

To manually apply the trailer brakes independently of the tractor brakes.