FREE 310T Air Brakes and Braking Systems Questions and Answers

Question 1

A technician is diagnosing an air brake system where the compressor cycles on and off too frequently.
The system builds to the correct cut-out pressure, but then pressure drops rapidly to the cut-in point with no brakes applied.
Which of the following is the MOST likely cause?

Accepted Answer

A leaking supply reservoir check valve

Answer

A saturated air dryer desiccant cartridge

Answer

A faulty foot valve (treadle valve)

Answer

A misadjusted slack adjuster on a service brake

Question 2

Which of the following BEST describes the operating principle of a spring brake chamber for parking and emergency braking?

Accepted Answer

A large coil spring provides the mechanical force to apply the brakes when air pressure is released or lost.

Answer

Air pressure is applied to a large coil spring, causing it to expand and apply the brakes.

Answer

The service brake application is controlled by spring force, while the parking brake is applied with air pressure.

Answer

Air pressure is required to both apply and release the parking brake mechanism.

Question 3

While performing a brake inspection, a technician measures the applied pushrod stroke of a standard, clamp-type, Type 30 brake chamber at 2.25 inches. According to CVSA (Commercial Vehicle Safety Alliance) out-of-service criteria, what is the correct action?

Accepted Answer

Place the vehicle out-of-service and adjust the slack adjuster.

Answer

Replace the brake chamber as it is overstroking.

Answer

No action is needed as this is within the acceptable limit.

Answer

Check the air pressure, as it is likely too low.

Question 4

What is the primary function of the tractor protection valve?

Accepted Answer

To prevent the tractor's air supply from being depleted by a major leak on the trailer side.

Answer

To apply the trailer brakes when the hand valve (trolley valve) is used.

Answer

To regulate the service brake application pressure to the trailer to prevent wheel lock-up.

Answer

To quickly release air from the trailer brake chambers after a brake application.

Question 5

A driver reports that the trailer ABS warning lamp on the dashboard is continuously illuminated, but the tractor ABS lamp functions normally (cycles on and off at startup). What is the MOST likely location of the fault?

Accepted Answer

A faulty wheel speed sensor or wiring on a trailer axle.

Answer

The brake treadle valve position sensor.

Answer

The main ABS electronic control unit (ECU) on the tractor.

Answer

The gladhand seals between the tractor and trailer.

Question 6

During the purge cycle of an air dryer, which of the following actions occurs to regenerate the desiccant material?

Accepted Answer

A small volume of dry air from a purge tank is back-flushed through the desiccant to expel moisture.

Answer

The compressor forces a high-pressure blast of hot, moist air through the desiccant.

Answer

The governor signals the compressor to reverse its rotation, pulling moisture out.

Answer

Heaters inside the air dryer are activated to bake the moisture out of the desiccant beads.

A technician is diagnosing an air brake system where the compressor cycles on and off too frequently.The system builds to the correct cut-out pressure, but then pressure drops rapidly to the cut-in point with no brakes applied.Which of the following is the MOST likely cause?

A technician is diagnosing an air brake system where the compressor cycles on and off too frequently.
The system builds to the correct cut-out pressure, but then pressure drops rapidly to the cut-in point with no brakes applied.
Which of the following is the MOST likely cause?