310T Air Brakes and Braking Systems 3

Question 1

What type of valve modulates air pressure to each wheel independently during ABS activation?

Accepted Answer

Modulator valve (ABS solenoid valve)

Answer

Relay valve

Answer

Quick-release valve

Answer

Limiting valve

Question 2

In a dual-circuit air brake system, which reservoir is pressurized first by the compressor?

Accepted Answer

Wet (supply) tank

Answer

Front (primary) circuit reservoir

Answer

Rear (secondary) circuit reservoir

Answer

Trailer reservoir

Question 3

What is the minimum air pressure at which the low-pressure warning device must activate per FMCSA regulations?

Accepted Answer

60 psi

Answer

45 psi

Answer

80 psi

Answer

90 psi

Question 4

A relay valve is used in air brake systems primarily to:

Accepted Answer

Shorten brake application and release time for remote chambers

Answer

Reduce air pressure to the front axle brakes

Answer

Protect the tractor air system from trailer air loss

Answer

Balance pressure between primary and secondary circuits

Question 5

On a combination vehicle, which valve automatically closes to protect the tractor air supply if trailer air pressure drops rapidly?

Accepted Answer

Tractor protection valve

Answer

Glad hand check valve

Answer

Double-check valve

Answer

Inversion valve

Question 6

What is the function of the inversion (fail-safe) valve used with spring brake chambers?

Accepted Answer

Inverts the pressure signal so spring brakes apply when service pressure is lost

Answer

Doubles the spring brake hold-off pressure for hill starts

Answer

Converts service brake application into spring brake application

Answer

Allows manual release of spring brakes without air

Question 7

Brake fade on a heavily loaded truck descending a long grade is MOST likely caused by:

Accepted Answer

Heat buildup reducing friction between lining and drum

Answer

Overloaded air reservoirs losing pressure

Answer

ABS modulator valve cycling too frequently

Answer

Slack adjuster over-travel beyond rated stroke