Chapter 3: Service Brake Subsystem

The “Service Brake Subsystem” chapter in the Ontario air brake test manual highlights the main braking system used during regular driving.

Ontario Air Brake Test - Chapter 3: Service Brake Subsystem

1 / 25

Why is it critical that brakes are correctly adjusted?

To reduce engine noise

Only to make the vehicle ride more smoothly

To ensure brake function is retained and legal requirements are met

To prevent tire wear only

2 / 25

What flexible component inside a service brake chamber moves when air pressure is applied?

Slack adjuster

Diaphragm

Pushrod return spring

Brake drum

3 / 25

In a dual-circuit air brake system, air is drawn from:

Only the primary tank

A single combined tank

Both primary and secondary tanks

Only the secondary tank

4 / 25

What component links the brake chamber pushrod to the brake assembly?

Slack adjuster

Brake pedal

Brake hose

Diaphragm

5 / 25

How does increased application pressure (for example, from 69 kPa to 552 kPa) affect pushrod stroke?

The stroke becomes zero

The stroke always remains the same

The stroke decreases

The stroke increases noticeably

6 / 25

What happens to brake force when pushrod stroke exceeds the adjustment limit?

Brake force drops significantly

Brake force increases excessively

Brake force moves to the steering axle only

Brake force remains unchanged

7 / 25

What are the two kinds of air brake chambers mentioned?

Front and rear chambers

Service and spring brake chambers

Primary and secondary chambers

Drum and disc chambers

8 / 25

What happens as the brake pedal is pressed harder?

The valve opens farther, increasing air pressure to the service brakes

The valve closes, reducing air pressure to the brakes

The air compressor turns off

The parking brakes automatically apply

9 / 25

What are the brakes used for normal stopping on vehicles with air brakes called?

Emergency brakes

Spring brakes

Parking brakes

Service brakes

10 / 25

Brake hoses and tubes used in air brake systems must:

Be the correct size and type

Be interchangeable regardless of size

All be made from metal only

All be colourless

11 / 25

What is the purpose of brake hoses and tubes in an air brake system?

Transmit electrical signals to dash gauges

Circulate coolant in the engine

Deliver compressed air to all components of the air brake system

Deliver fuel to the engine

12 / 25

In common brake designs, why can pushrod stroke length be measured?

The chambers are transparent

Stroke length is always hidden inside the drum

The pushrod is monitored electronically only

Some brake linkage components are exposed

13 / 25

What is a key rule regarding pushrod stroke?

Stroke should be adjusted only when brakes are new

Stroke length does not need to be checked

You must not let the pushrod stroke exceed the adjustment limit

You must always set the stroke to the maximum possible

14 / 25

When air pressure is released from a service brake chamber, what returns the pushrod to its original position?

The parking brake mechanism

The driver pulling back the pedal

The spring inside the chamber

The slack adjuster

15 / 25

Why is it important to correctly identify brake type and chamber size?

To select the proper tire pressure

To adjust steering alignment

To choose the correct engine oil

To determine the correct pushrod stroke-adjustment limit

16 / 25

Who is allowed to perform brake re-adjustments on manual and automatic slack adjusters?

Only the vehicle owner

Only certified technicians

Any mechanic without specific certification

Any driver with a licence

17 / 25

When you press the brake pedal, what causes the pushrod in the brake chamber to move out?

Hydraulic fluid pressure

Compressed air filling the chamber and moving the diaphragm

A mechanical cable pulling on the rod

Gravity acting on the rod

18 / 25

What is the function of an air brake chamber?

Store engine coolant

Control the vehicle’s electrical system

Convert compressed air into mechanical force to apply the brakes

Lubricate the brake components

19 / 25

Why must brake linkage be readjusted as brakes wear?

To change brake shoe type

To reduce air tank size

To increase fuel economy

To keep pushrod stroke within its normal operating range

20 / 25

What does pressing the brake pedal directly control?

The electrical system voltage

The air pressure applied to the service brakes

The parking brake application

The fuel flow to the engine

21 / 25

Why is a dual-circuit brake design used?

To reduce the need for air compressors

To eliminate the need for regular inspections

So that if one circuit fails, the other circuit still operates some brakes

To increase fuel efficiency

22 / 25

What are clamp-type brake chambers?

Chambers held together by a clamp assembly

Chambers welded permanently

Chambers made only of plastic

Chambers that cannot be disassembled

23 / 25

What is the primary function of the brake pedal in an air brake system?

Release the spring brakes only

Apply the service brakes

Control engine braking only

Apply the parking brakes only

24 / 25

The front wheel-limiting valves (where used) have what function?

Lock the front wheels during braking

Disable the rear brakes when turning

Reduce the force of the service brakes on the front steering axle

Increase fuel delivery to the engine

25 / 25

What is “pushrod stroke”?

The diameter of the brake drum

The distance the pushrod travels out of the brake chamber

The speed at which the wheels turn

The amount of air in the reservoir

Your score is

This section explains how the service brakes work: air pressure applied to brake chambers activates the brakes on each wheel. It details key components such as brake pedals, chambers, push rods, and slack adjusters. Drivers are taught how to identify proper function, recognize warning signs of malfunction, and understand the importance of regular inspections. Mastering this chapter is essential for passing the Ontario air brake test and for ensuring safe, controlled stops when operating vehicles equipped with air brakes.