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 important to correctly identify brake type and chamber size?

To choose the correct engine oil

To determine the correct pushrod stroke-adjustment limit

To adjust steering alignment

To select the proper tire pressure

2 / 25

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

The driver pulling back the pedal

The slack adjuster

The parking brake mechanism

The spring inside the chamber

3 / 25

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

Only certified technicians

Only the vehicle owner

Any driver with a licence

Any mechanic without specific certification

4 / 25

Why is it critical that brakes are correctly adjusted?

Only to make the vehicle ride more smoothly

To ensure brake function is retained and legal requirements are met

To reduce engine noise

To prevent tire wear only

5 / 25

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

Gravity acting on the rod

Compressed air filling the chamber and moving the diaphragm

A mechanical cable pulling on the rod

Hydraulic fluid pressure

6 / 25

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

Stroke length is always hidden inside the drum

The chambers are transparent

Some brake linkage components are exposed

The pushrod is monitored electronically only

7 / 25

Brake hoses and tubes used in air brake systems must:

All be colourless

All be made from metal only

Be the correct size and type

Be interchangeable regardless of size

8 / 25

What is the function of an air brake chamber?

Store engine coolant

Lubricate the brake components

Convert compressed air into mechanical force to apply the brakes

Control the vehicle’s electrical system

9 / 25

Why is a dual-circuit brake design used?

To increase fuel efficiency

To eliminate the need for regular inspections

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

To reduce the need for air compressors

10 / 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

11 / 25

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

A single combined tank

Both primary and secondary tanks

Only the primary tank

Only the secondary tank

12 / 25

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

Spring brakes

Parking brakes

Service brakes

Emergency brakes

13 / 25

What does pressing the brake pedal directly control?

The parking brake application

The electrical system voltage

The air pressure applied to the service brakes

The fuel flow to the engine

14 / 25

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

Slack adjuster

Diaphragm

Brake drum

Pushrod return spring

15 / 25

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

Disable the rear brakes when turning

Increase fuel delivery to the engine

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

Lock the front wheels during braking

16 / 25

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

Control engine braking only

Apply the service brakes

Apply the parking brakes only

Release the spring brakes only

17 / 25

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

Brake force increases excessively

Brake force drops significantly

Brake force moves to the steering axle only

Brake force remains unchanged

18 / 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 increases noticeably

The stroke decreases

19 / 25

What are the two kinds of air brake chambers mentioned?

Service and spring brake chambers

Primary and secondary chambers

Drum and disc chambers

Front and rear chambers

20 / 25

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

Slack adjuster

Brake pedal

Brake hose

Diaphragm

21 / 25

What happens as the brake pedal is pressed harder?

The valve closes, reducing air pressure to the brakes

The air compressor turns off

The parking brakes automatically apply

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

22 / 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

23 / 25

What is a key rule regarding pushrod stroke?

Stroke should be adjusted only when brakes are new

You must not let the pushrod stroke exceed the adjustment limit

Stroke length does not need to be checked

You must always set the stroke to the maximum possible

24 / 25

What are clamp-type brake chambers?

Chambers that cannot be disassembled

Chambers held together by a clamp assembly

Chambers made only of plastic

Chambers welded permanently

25 / 25

What is “pushrod stroke”?

The speed at which the wheels turn

The diameter of the brake drum

The distance the pushrod travels out of the brake chamber

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.