Air Brake Test Pre-trip Inspection Procedures 2

Question 1

During a pre-trip air brake inspection, at what pressure should the low air pressure warning signal activate?

Accepted Answer

Before air pressure drops below 60 psi

Answer

At exactly 90 psi

Answer

Only when pressure reaches 0 psi

Answer

At 75 psi during engine-off testing only

Question 2

What is the correct procedure to test the spring brakes during a pre-trip inspection?

Accepted Answer

Charge the system, chock wheels, release service brakes, pull the parking brake knob, and attempt to move the vehicle

Answer

Apply service brakes at full pressure and measure stopping distance

Answer

Release all air from the system and verify the vehicle does not roll

Answer

Start the engine and check that the spring brake light extinguishes within 30 seconds

Question 3

How do you test the tractor protection valve during a pre-trip inspection?

Accepted Answer

Close the shut-off valves on the rear, reduce trailer air pressure to trigger the valve, and confirm it closes

Answer

Apply service brakes repeatedly until trailer air line pressure drops below 30 psi

Answer

Disconnect the trailer and verify tractor brakes function independently

Answer

Start the engine and observe that trailer supply pressure builds to 100 psi within 60 seconds

Question 4

What is the acceptable pressure drop rate with service brakes applied during the pre-trip air brake leak test?

Accepted Answer

Less than 3 psi per minute for single vehicles; less than 4 psi per minute for combination vehicles

Answer

Less than 10 psi per minute for any vehicle type

Answer

No pressure drop is acceptable in any vehicle

Answer

Less than 5 psi per minute regardless of vehicle configuration

Question 5

When inspecting the air compressor belt during a pre-trip, what should you check for?

Accepted Answer

Cracks, fraying, proper tension, and correct alignment

Answer

Belt color and manufacturer markings

Answer

Belt temperature using a thermal gun

Answer

Only the presence of the belt — condition is assessed only during maintenance

Question 6

During a pre-trip, you notice the air pressure gauge is fluctuating rapidly and erratically. What could this indicate?

Accepted Answer

A faulty gauge, a failing compressor governor, or a significant air leak in the system

Answer

Normal compressor cycling during warm-up

Answer

The automatic drain valves are functioning correctly

Answer

The ABS system is self-testing