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

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

The spring is under very high tension and can release violently

The chambers are sealed with permanent glue

The chambers are too heavy to move

The chambers contain flammable fluid

2 / 30

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

Turn off the spring brake control valve

Add more air pressure to reactivate the chamber

Have the vehicle inspected and repaired immediately

Continue driving normally until the next scheduled service

3 / 30

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

Smaller because it uses less air

The same size and appearance

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

Only used on the front axle

4 / 30

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

Inside the air dryer

Nearest the pushrod end

Farthest from the pushrod end

In the middle of the chamber

5 / 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 engine will automatically shut down

The spring brakes will begin to apply automatically

The air compressor will stop working permanently

The service brakes will automatically cool

6 / 30

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

Three

One

Four

Two

7 / 30

How are spring brakes applied?

They apply when air pressure leaves the brake chamber

They apply only when the driver presses the brake pedal

They apply only when the vehicle is turned off

They apply when air pressure builds up in the brake chamber

8 / 30

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

Because the valve is only decorative

Because the valve must be removed daily

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

Because it must be adjusted during driving

9 / 30

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

To control the air compressor

To adjust the parking brake

To apply only the spring brakes

To apply the service brakes

10 / 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 increases air supply to the service brakes

It shuts down the engine

It opens the air dryer purge valve

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 service brakes cool down

The parking brake is fully released

12 / 30

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

By an electronic solenoid only

By a hydraulic locking device

By a large external coil spring

By a mechanical means inside the chamber

13 / 30

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

To replace the need for regular brake inspections

To increase fuel efficiency during highway driving

To cool the service brakes during long downhill runs

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

14 / 30

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

It makes the spring brakes apply too quickly

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

It improves spring brake stopping power

It causes the spring brakes to overheat

15 / 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 shutting off the engine

By using the spring brake control valve

16 / 30

What is a DD3 Safety Actuator?

A type of air compressor governor

A specialized front axle service brake

A device used only on trailers with hydraulic brakes

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

17 / 30

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

Handwheel valve located on the steering column

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

Floor-mounted toggle switch with a green knob

Foot-operated valve with a red round button

18 / 30

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

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

Turn the valve clockwise to release the spring brakes

Press the brake pedal while turning off the ignition

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

19 / 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

20 / 30

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

The knob locks in the pushed-in position

The knob becomes loose and spins

The knob changes color

The knob pops out

21 / 30

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

Disconnect and reconnect the air lines

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

22 / 30

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

To keep the spring brakes from starting to apply

To disable the parking brake control valve

To make the compressor run faster

To prevent the service brakes from overheating

23 / 30

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

The service brakes automatically release

The spring brakes fully release

The spring brakes start to apply automatically

The compressor shuts down immediately

24 / 30

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

By the visible protrusion of the caging bolt or similar mechanism

By the chamber being smaller in size

By the chamber being painted a different color

By the absence of any air lines

25 / 30

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

Off-road construction equipment only

Buses and motor coaches

Light-duty pickup trucks

Passenger cars

26 / 30

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

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

A cab suspension control with a green knob

A trailer exhaust valve with a red lever

A front axle lock valve with a white knob

27 / 30

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

To increase the force of the spring brake

To manually compress and disable the spring brake

To connect two chambers together

To automatically adjust the brake shoes

28 / 30

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

It only affects service brakes, not spring brakes

It is greatly increased

It remains unchanged

It is reduced

29 / 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 designed to be serviced by drivers

It is under low tension and safe to handle

30 / 30

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

About 690 kPa (100 psi)

About 414 kPa (60 psi)

About 276 kPa (40 psi)

About 138 kPa (20 psi)

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.