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

Faulty compressor unloader valve

Answer

Stuck open purge valve solenoid

Answer

Governor set too low

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

Low reservoir pressure on the primary circuit

Answer

A seized left front brake chamber push rod

Answer

A leaking right front service brake chamber diaphragm

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

2 psi

Answer

4 psi

Answer

6 psi

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

Low spring brake modulator pressure

Answer

Air compressor overheating and shutting off

Answer

Trailer supply valve leaking externally

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

Vernier caliper

Answer

Dial indicator mounted to the chamber body

Answer

Brake angle gauge

Question 6

A quick-release valve fails to exhaust air from the brake chambers quickly. Which symptom will the driver notice?

Accepted Answer

Brake drag due to slow pressure release

Answer

High pedal effort during initial application

Answer

Premature spring brake application

Answer

Air dryer cycling too frequently

Question 7

An S-cam brake assembly shows uneven lining contact, with the leading edge of the lining worn more than the trailing edge. This MOST likely indicates:

Accepted Answer

Weak or broken return springs allowing the cam to over-rotate

Answer

Incorrect lining type installed

Answer

Cam bushings worn allowing the cam to shift axially

Answer

A cracked brake drum