CDL Air Brake - Commercial Driver's License Air Brakes Air Pressure and Leakage Tests Questions and Answers

Question 1

During an air brake pre-trip inspection on a combination vehicle, you perform the applied leakage test.
After the initial pressure drop, what is the maximum allowable decrease in air pressure over a one-minute period?

Accepted Answer

4 psi

Answer

2 psi

Answer

3 psi

Answer

5 psi

Question 2

A driver is performing the air pressure buildup test. With the engine at normal operating RPMs, the pressure must build from 85 to 100 psi within what timeframe for a dual air brake system?

Accepted Answer

45 seconds

Answer

30 seconds

Answer

60 seconds

Answer

90 seconds

Question 3

You are conducting a static leakage test on a straight truck. The procedure involves fully charging the system, turning off the engine, and releasing all brakes. After the initial drop, the air pressure should not drop more than:

Accepted Answer

2 psi in one minute

Answer

4 psi in one minute

Answer

3 psi in one minute

Answer

1 psi in one minute

Question 4

A driver is testing the low air pressure warning system. After turning the engine off and the key to the 'on' position, the driver begins to fan the brake pedal. The warning light and buzzer MUST activate at or before what pressure?

Accepted Answer

60 psi

Answer

85 psi

Answer

45 psi

Answer

75 psi

Question 5

While testing the automatic application of the spring brakes, a driver fans the brake pedal to lower the system's air pressure. At what approximate pressure range should the parking brake valve pop out, causing the spring brakes to engage?

Accepted Answer

20-45 psi

Answer

80-100 psi

Answer

60-75 psi

Answer

Below 20 psi

Question 6

Which of the following scenarios describes a failed air pressure buildup test, requiring immediate mechanical attention?

Accepted Answer

The air pressure takes 55 seconds to build from 85 to 100 psi.

Answer

The governor cuts out at 130 psi.

Answer

The air pressure builds from 85 to 100 psi in 40 seconds.

Answer

The low air warning buzzer activates at 65 psi.

During an air brake pre-trip inspection on a combination vehicle, you perform the applied leakage test.After the initial pressure drop, what is the maximum allowable decrease in air pressure over a one-minute period?

During an air brake pre-trip inspection on a combination vehicle, you perform the applied leakage test.
After the initial pressure drop, what is the maximum allowable decrease in air pressure over a one-minute period?