DTC Brake Systems 5

Question 1

Under the CVSA out-of-service criteria, what share of a vehicle's service brakes found defective or out of adjustment puts the vehicle out of service?

Accepted Answer

20% or more

Answer

Under the CVSA 20 percent criterion, a vehicle goes out of service when defective brakes reach 20% or more of its service brakes.

Question 2

What does a pressure protection valve do in an air brake system?

Accepted Answer

It keeps air in the brake reservoirs by closing an accessory circuit when pressure falls below its set point

Answer

Pressure protection valves close off non-brake accessories so a leak there cannot drain air the brakes need.

Question 3

An air disc brake has uneven inboard/outboard pad wear and the caliper fails to release fully. What is the most likely cause?

Accepted Answer

Seized or binding caliper guide pins

Answer

Binding guide pins stop the caliper from floating, which causes uneven pad wear and drag.

Question 4

A trailer built after March 1, 1998 (through 2009) has its ABS warning lamp lit after power-up. Where is that external lamp usually mounted?

Accepted Answer

On the left rear side of the trailer

Answer

Federal rules called for an external trailer ABS lamp on the left side near the rear so the driver can see it in the mirror.

Question 5

What does the governor do when system pressure reaches cut-out pressure?

Accepted Answer

It sends air to the compressor unloader mechanism so the compressor stops pumping

Answer

At cut-out the governor pressurizes the unloader, which puts the compressor in its unloaded cycle until cut-in.

DTC - Diesel Technician Certification Practice Test

DTC - Diesel Technician Certification Practice Test

DTC Brake Systems 5