310T Air Brake Systems Diagnosis 2

Question 1

A truck's air dryer purge valve is constantly exhausting air. What is the MOST likely cause?

Accepted Answer

Excessive compressor oil carry-over clogging the desiccant

Answer

Excessive oil carry-over from a worn compressor saturates the desiccant cartridge, reducing its efficiency and causing the purge cycle to vent continuously.

Question 2

During a brake application, the left front wheel locks up while the right front remains normal. This symptom MOST likely indicates:

Accepted Answer

A stuck open ABS modulator valve on the left front

Answer

A stuck open ABS modulator inlet valve prevents pressure release to the affected wheel, causing it to lock while the ABS system fails to cycle.

Question 3

When performing a static leakage test on a straight truck, the maximum allowable pressure drop per minute for the service brake system is:

Accepted Answer

3 psi

Answer

FMCSA regulations allow a maximum of 3 psi drop per minute for single-vehicle service brake systems during a static leakage test.

Question 4

A driver reports that the spring brakes apply automatically when going downhill on a long grade. The MOST likely cause is:

Accepted Answer

System air pressure dropping below the low-pressure warning threshold

Answer

If sustained brake application drains the reservoir pressure below approximately 60 psi, the spring brakes automatically apply to prevent brake fade.

Question 5

What tool is used to accurately measure the push rod stroke of a brake chamber to determine if it exceeds the adjustment limit?

Accepted Answer

Steel ruler applied at full brake application

Answer

A steel ruler placed against the chamber body with the push rod at full application gives the stroke reading that is compared to the maximum stroke limit.

(310t) Truck and Coach Technician Certification Practice Test

(310t) Truck and Coach Technician Certification Practice Test

310T Air Brake Systems Diagnosis 2