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WorksheetsBrakes 204 pretest winter 2025
Total questions: 70
Worksheet time: 8hrs 5mins
Excessive heat caused by overuse of the service brakes can cause
Modulating control valve to wear out.
The brakes to fade.
A brake line to split
A typical air brake system is fully charged at
75 psi
150 psi
120 psi
If you do not have an automatic tank drain, When should you drain your air tanks?
After every four hours of service
At the end of each working day
Once a week
Air braking takes more time than hydraulic braking because air
Brakes use different brake drums.
Brakes require heavier return springs.
Takes more time to flow through lines then hydraulic fluid
When you apply the brake pedal, the brake shoes and linings are pressed against the
Brake drum.
Slack adjuster.
S-cam.
During normal driving, spring brakes are usually held back by
Air pressure.
Springs.
Bolts and braces.
What is the first thing you should do if the low air pressure warning comes on?
Upshift.
Downshift.
Stop.
The air compressor should stop pumping air into the air tanks at
125 psi
100 psi
150 psi
Repeatedly pressing and releasing (fanning) the brake pedal may result in
A buildup of brake air pressure.
A loss of brake air pressure.
No change in brake air pressure.
To check the slack adjusters on S-cam drum brakes, you should first
Stop on level ground and apply the parking brakes.
Park on level ground, chock the wheels, and release the parking brakes.
Park on level ground and drain off the air pressure.
If your truck or bus has dual parking control valves, you can use air pressure from a separate tank to
Stay parked twice as long without using up service air pressure.
Balance the service brake system when you are parked.
Release the spring brakes.
Why should air tanks be drained?
Your brakes may fail because of water freezing.
Your transmission fluid may drain out.
Your left-side brake will cease to operate.
If the air compressor should develop a leak, what will keep the air in the tanks?
The emergency relay valve
The tractor protection valve
The one-way check valve
You’ll know that your brakes are fading if
You have to press the brake pedal harder than usual to control your speed.
You release the brake pedal and your speed increases.
The brakes feel spongy when you apply pressure.
The low air pressure warning signal should come on before the pressure in the air tanks fall below
55 psi.
80 psi.
70 psi.
Tractor and straight truck spring brakes will come fully on when the pressure drops to a range of
15 to 40 psi.
20 to 45 psi.
60 to 80 psi.
Excessive use of the service brakes may result in overheating, which can lead to
improper adjustment of the S-cams
Increased contact between the brake drums and the brake linings
Expansion of the brake drums.
IF the air compressor should develop a leak, what keeps the air in the tank from immediately leaking out?
The one way check valve
the emergency relay valve
the tractor protection valve
-
The modulating control valve allows you to gradually control the:
spring breaks
amount of pressure in the break system
front breaks
trailer brakes
When you put the brakes on by pushing down on the break pedal:
compressed air is let go out to the system
Air pressure is applied to the brake pads
The air pressure is reduced to the brake pads
Which of these is the most important thing to remember about emergency braking.
Never do it without downshifting first
If the wheels are skidding, you cannot control the vehicle
Disconnecting the steering axle brakes will help keep vehicle in a straight line during emergency breaking.
The service brake applies and releases
The parking brake when you use the parking brake control
In the event of an emergency
The brakes when you use the brake pedal during normal driving
-
The air supply pressure gauge shows how much pressure
Is going to the brake chambers
You have used in this trip
is in the air tanks
that is supplied to ABS modules
Modern air brake system are 3 different systems combined together. They are service, parking and ______ brakes.
foot
S-cam
emergency
What is a dual air brake system?
One operates the front brakes, the other the back
one for daytime, the other for night driving
One for each side of the vehicle
The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than:
2 psi in 45 sec
1 psi in 1 min
4 psi in 1 min
The air compressor governor controls:
air pressure applied to the brakes
when air is pumped into the air storage tanks
The speed (allowance) of the air compressor
The____controls the amount of air pumped into the tanks, which is measured in terms of pounds per square inch or psi
governor
spring
air brake
Which vehicles must have low air pressure warning signals?
Those built after 2010 must have low air pressure warning signals
Those built after 2005 must have low air pressure warning signals
All vehicles with air brakes currently in operation must have low air pressure warning signals
Warning signals are optional
Spring brakes are
All of the these
brakes that come on automatically on a truck or tractor when the psi drops too low
made up of powerful springs that are held in back by air pressure while you are driving
not going to have full effect until your psi drops to a certain range--often 20 to 30 psi
How do brakes work on a long, steep downgrade:
As the main braking mechanism, with the engine braking effect as an emergency "back-up"
As a supplement to the braking effect of your engine
As the main braking mechanism
Not applicable --there is no braking effect involved in a downgrade
Which of the following does ABS do?
Increases your normal braking capability
Activates when the wheels are locking up
Decreases your normal braking capability
Shortens your stopping distance
Primary brake circuits are commonly color coded as what color air lines?
Blue
Green
Black
Red
What type of valves are critical devices used to speed up the flow of air during brake applications and release?
Relay
Exhaust
Air brake
Anti-compounding
Two color-coded flexible hoses connect the tractor and trailer air system. What color is used for the supply/emergency circuit?
Yellow
Red
Green
Blue
What type of valve is this?
Quick Release Valve
Relay Valve
Modulator Valve
Safety Valve
Air dryers use a replaceable desiccant cartridge to trap oil and water discharged from the compressor by a process known as _____________.
combustion
pressure-protection
adsorption
consumption
What type of valve is this?
Quick Release Valve
Relay Valve
ABS Modulator Valve
Safety Valve
The primary function of _____________valve is to prevent a rapid loss of air from the tractor during a trailer breakaway condition or when either the tractor or trailer develops a severe air leak.
quick-release
tractor protection
trailer brake control
double check
What is the name of this component?
Quick Release Valve
Air Governor
Air Dryer
Safety Valve
Air pressure from the foot valve (signal air) is supplied to a service-control port on the _______valve.
relay
proportioning
quick-release
service brake control
What color is the octagonal-shaped trailer supply valve used to control the tractor protection system?
Red
Blue
Green
Yellow
What is the name of this part?
Quick Release Valve
Air Governor
Air Dryer
Safety Valve
Which of the following are the air couplers attached to the trailer hoses connecting the tractor and trailer air systems?
Circuits
Boosters
Governors
Gladhands
The size of _________is determined by the number of axles on the truck/tractor and trailer.
reservoirs
compressors
governors
cylinders
Compressors are usually __________.
located in the cylinder head
engine driven
normally closed
like an in-line filtration system
Which of the following is responsible for removing oil passed into the air supply by the compressor?
Select one:
a.Exhaust port
b.Service chamber
c.Air dryer
d.Air reservoir
What is the basic principle of air brake operation?
Friction is used to apply and release the brakes.
Electricity is used to apply and release the brakes.
Hydraulic fluid is used to apply and release the brakes.
Compressed air is used to apply and release the brakes.
Name two essential components of an air brake system .
Compressor
governor
intercooler
blower
Describe the role of an air compressor in an air brake system and how it operates.
The air compressor pressurizes the air used to operate the brakes by drawing in air and compressing it to a high pressure.
The air compressor is used to cool down the engine
The air compressor is responsible for steering the vehicle
The air compressor releases air to slow down the vehicle
What are some common maintenance tasks for air brake systems?
Checking for air leaks
draining oil
inspecting driveline
Refilling the windshield washer fluid
How can air leaks in an air brake system be identified first?
By ignoring the issue and continuing to operate the vehicle
By listening for hissing or escaping air and locating the source of the leak to replace or repair the damaged component.
By adding more air to the system till noise stops
By replacing the entire air brake system
Tech A says brake foundations are the braking components found at the wheel ends. Tech B says the cam brakes system use a C-shaped cam between 2 rollers, who is correct.
Tech A
Tech B
both
neither
what component stops the air compressor from charging the air system?
governor
Check valve
air dryer
none of these components
What safety measures should be followed when working on air brake systems?
Ignoring manufacturer's guidelines
Starting work without depressurizing the system
Wearing protective gear, depressurizing the system before starting work, and following manufacturer's guidelines
Not wearing any protective gear
Why is it important to drain moisture from air brake systems and how can it be done effectively?
To improve fuel efficiency, and it can be done effectively by releasing air from the system
To reduce noise from the brakes, and it can be done effectively by adding water to the air tanks
To increase the speed of the vehicle, and it can be done effectively by adding more air to the system
To prevent corrosion and freezing, and it can be done effectively by regularly draining the air tanks and using air dryer systems.
Other than water, what else does a air dryer remove from the air being supplied to the brake and suspension system?
NO2
carbon
DEF
oil
rear axle brakes
front brakes
what is the term used to describe the run time for a compressor
duty cycle
discard time
output cycle
none of these
What does CFM stand for?
Cubic Feet Per Minute
Chrome Fastened Mount
Cubic Feet per Mile
Cubed for Measurement
Can the turbo supply air to the compressor in certain applications?
True
false
Do you have to set the cut in/cut out adjustments levels for a Governor before operation?
true
false
What is the most air pressure allowed by government regulations before a safety valve must discharge air?
100
200
150
250
Why do we use "safety valves"?
to protect air circuit components
to measure air pressure
to stop safely
none of these answers
When a safety valve works, how do we know?
dash indicator
LED light
audible alert
bad odor
Does the air dryer purge?
true
false
Another name for a "air tank" in a air brake circuit?
(a)
Braking odors are typically related to overheated________
Brake chambers
Brake drums
Bushings
Brake linings
Which of the following is identified by the sudden exhaust of air draining from the dryer?
purging
unloading
snubbing
burnishing
How does the ROTO-PETAL DISC BRAKE enhance braking performance?
lower stopping distance
Ensures highly responsive braking
Increases heat dissipation and reduces brake pad wearing
All of the above
