Chapter 4: Spring Brake Subsystem

The “Spring Brake Subsystem” chapter in the Ontario air brake test manual focuses on the emergency and parking brake functions of air brake systems.

Ontario Air Brake Test - Chapter 4: Spring Brake Subsystem

1 / 30

What happens when system air pressure drops below about 414 kPa (60 psi)?

The spring brakes start to apply automatically

The compressor shuts down immediately

The service brakes automatically release

The spring brakes fully release

2 / 30

What is the name of a brake chamber that includes both service brake and spring brake sections?

Spring brake chamber

Parking-only chamber

Service-only chamber

Dual-diaphragm chamber

3 / 30

How are spring brakes applied?

They apply only when the driver presses the brake pedal

They apply when air pressure leaves the brake chamber

They apply only when the vehicle is turned off

They apply when air pressure builds up in the brake chamber

4 / 30

On what types of vehicles are DD3 brake chambers commonly found?

Buses and motor coaches

Passenger cars

Light-duty pickup trucks

Off-road construction equipment only

5 / 30

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

To apply the service brakes

To adjust the parking brake

To apply only the spring brakes

To control the air compressor

6 / 30

When system pressure falls below its normal operating range (around 414 kPa or 60 psi), what is the key point drivers must remember?

The service brakes will automatically cool

The engine will automatically shut down

The air compressor will stop working permanently

The spring brakes will begin to apply automatically

7 / 30

What is the purpose of a “caging bolt” in a spring brake chamber?

To automatically adjust the brake shoes

To increase the force of the spring brake

To connect two chambers together

To manually compress and disable the spring brake

8 / 30

Compared to a regular service brake chamber, a spring brake chamber is:

Smaller because it uses less air

Larger because it has an additional section to house the coil spring

The same size and appearance

Only used on the front axle

9 / 30

How can a driver recognize a disabled (caged) spring brake chamber?

By the chamber being smaller in size

By the chamber being painted a different color

By the visible protrusion of the caging bolt or similar mechanism

By the absence of any air lines

10 / 30

Why should drivers never attempt to service or repair any air brake chamber containing a large coil spring?

The chambers are too heavy to move

The chambers contain flammable fluid

The chambers are sealed with permanent glue

The spring is under very high tension and can release violently

11 / 30

What occurs when the spring brake control valve exhausts the air holding the spring brakes released?

The spring brakes apply suddenly, causing an uncontrolled stop

The compressor stops building air

The parking brake is fully released

The service brakes cool down

12 / 30

What is a DD3 Safety Actuator?

A type of air compressor governor

A specialized front axle service brake

A type of parking and emergency brake chamber that does not use a large coil spring

A device used only on trailers with hydraulic brakes

13 / 30

How can the spring brakes be applied in an emergency when the service brakes fail?

By turning on the headlights

By pumping the brake pedal repeatedly

By using the spring brake control valve

By shutting off the engine

14 / 30

Which statement about the large coil spring inside a spring brake chamber is correct?

It is only used on steer axle brakes

It is under high tension and can be hazardous if it fails

It is under low tension and safe to handle

It is designed to be serviced by drivers

15 / 30

On most vehicles, how is the spring brake control valve operated to release the spring brakes?

Pull the valve out to supply air and release the spring brakes

Push the valve in to supply air and release the spring brakes

Press the brake pedal while turning off the ignition

Turn the valve clockwise to release the spring brakes

16 / 30

What happens to the spring brake control valve knob when the spring brakes apply automatically due to low air pressure?

The knob changes color

The knob becomes loose and spins

The knob locks in the pushed-in position

The knob pops out

17 / 30

What is the primary purpose of spring brakes on vehicles with air brakes?

To cool the service brakes during long downhill runs

To provide parking and emergency braking if the service brake system fails

To replace the need for regular brake inspections

To increase fuel efficiency during highway driving

18 / 30

What additional control might some trucks and tractors have for their parking brakes?

A front axle lock valve with a white knob

A cab suspension control with a green knob

A trailer exhaust valve with a red lever

A tractor parking-brake control valve with a round blue knob

19 / 30

How is the brake locked in the applied position in a DD3 brake chamber?

By a mechanical means inside the chamber

By a large external coil spring

By an electronic solenoid only

By a hydraulic locking device

20 / 30

What is required to release the brakes on a DD3 system after operating the control valve?

Press the brake pedal for three to five seconds

Pump the brake pedal repeatedly for one minute

Turn off the ignition and restart the engine

Disconnect and reconnect the air lines

21 / 30

What does the spring brake control valve do automatically when system pressure drops below about 414 kPa (60 psi)?

It exhausts the remaining air holding the spring brakes released

It opens the air dryer purge valve

It increases air supply to the service brakes

It shuts down the engine

22 / 30

Why must drivers be familiar with the type of spring brake control valve used in their vehicle?

Because the valve must be removed daily

Because the valve is only decorative

Because some vehicles may use different types (push/pull or toggle) and functions

Because it must be adjusted during driving

23 / 30

How much air pressure is normally required to release (compress or “cage”) the spring in a spring brake chamber?

About 414 kPa (60 psi)

About 138 kPa (20 psi)

About 690 kPa (100 psi)

About 276 kPa (40 psi)

24 / 30

What happens to spring brake effectiveness if the foundation brakes are out of adjustment?

It is greatly increased

It remains unchanged

It is reduced

It only affects service brakes, not spring brakes

25 / 30

What type of valve is normally used as the spring brake (parking and emergency) control valve?

Foot-operated valve with a red round button

Push/pull type valve with a yellow, four-sided knob

Floor-mounted toggle switch with a green knob

Handwheel valve located on the steering column

26 / 30

What effect does poor brake adjustment have on spring brake performance?

It reduces the ability of spring brakes to stop or hold a vehicle

It causes the spring brakes to overheat

It makes the spring brakes apply too quickly

It improves spring brake stopping power

27 / 30

What should a driver do after noticing a disabled spring brake chamber?

Continue driving normally until the next scheduled service

Add more air pressure to reactivate the chamber

Turn off the spring brake control valve

Have the vehicle inspected and repaired immediately

28 / 30

How many air line connections does a DD3 brake chamber have?

One

Three

Two

Four

29 / 30

Why is it important to ensure there is enough air pressure before driving a vehicle with spring brakes?

To make the compressor run faster

To prevent the service brakes from overheating

To keep the spring brakes from starting to apply

To disable the parking brake control valve

30 / 30

Where is the service brake section located on a spring brake chamber?

Inside the air dryer

Farthest from the pushrod end

Nearest the pushrod end

In the middle of the chamber

Your score is

Spring brakes automatically engage when air pressure drops to a dangerous level, ensuring the vehicle can be safely stopped even if the main system fails. This chapter explains the components involved, such as the spring brake chambers and parking brake controls, and their role in vehicle safety. Understanding how to properly use, test, and maintain spring brakes is crucial for passing the Ontario air brake test and for preventing unintentional vehicle movement, especially on inclines or during emergencies.