ASD AIR BRAKES STUDY MATERIAL

This is the study material for the Air Brakes test. Please study it until you are comfortable with the material, and then proceed to the practice tests.

The driver must be able to see a warning before air pressure in the service air tanks falls below*

805550

To check the brake slack on S-cam brakes , you should park on*

Level ground, chock the wheel, and release the parking brakesA slight grade , release the parking brakes , and apply the service brakeswatching for vehicle movementLevel ground and apply the parking brakes

The air brake system for a straight truck or bus should not leak at a rate of more than _______ psi per minute with the engine off and the brakes released*

1 psi2 psi3 psi

The air loss rate for a straight truck or bus with the engine off and the brake on should not be more than*

3 psi in one minute2 psi in 45 seconds1 psi in one minute

If your vehicle has an alcohol evaporator, it is there to*

Eliminate the need for daily tank drainingReduce the risk of ice in air brake valves in cold weatherRid the wet tank of alcohol that condenses and sits at the bottom

How should you check that your service brakes are working properly?*

Park on level ground, chock the wheels, engage the parking brake and shut the engine offPark on a slight incline, drain off air pressure, set the parking brakes and check for movementWait for normal air pressure, release the parking brake, move the truck forward slowly, and apply the brake firmly using the brake pedal

The air supply pressure gauge shows how much pressure*

Is going to the brake chambersIs in the air tanksYou have used in this trip

Why should you drain water from compressed air tanks?*

Water cools the compressor too muchThe boiling point reduces braking powerWater can freeze in cold weather and cause brake failure

The safety valve is set to automatically reduce pressure at ___ psi*

15010050

If air pressure does not build up fast enough within the correct amount of time*

Your air pressure may drop too low during drivingYou should be ready to use your parking brake to help stopThe alcohol container may be low

How should you check that the spring brakes come on when air pressure in the system drops below a certain level?*

Park on level ground, wait for normal air pressure, release the parking brake, move the truck forward slowly and apply the brakes firmly using the brake pedal.Park on a slight incline, drain off air pressure, set parking brakes and check for movement.Park on level ground, chock the wheels, release the parking brake when you have enough air pressure, shut the engine off, and repeatedly press and release the brake pedal

For air brake systems in good condition, the air compressor should start pumping at about ____ psi*

100125150

To test air service brake, you should*

Brake firmly when slowly moving forwardsStop the vehicle, put it in low gear, depress the service brake, and then gently pull against the brakeBrake firmly when slowly moving backwards

If you do not have automatic tank drains, how often should you drain the oil and water from the bottom of the compressed air storage air tanks?*

After every four hours of serviceOnce a weekAt the end of each day of driving

When you apply the brakes, the brake shoes/linings are pressed against the:*

S-camSlack adjusterBrake drum

With air brake vehicles, the parking brakes should be used:*

As little as possibleWhenever you leave the vehicle unattendedOnly during pre-trip inspections

All air brake equipped vehicles have*

An air use gaugeA backup hydraulic systemAn air supply pressure gauge

The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, such as:*

Spring pressureAir pressureHydraulic pressure

The parking or emergency brakes of trucks and buses can be legally held on by________ pressure*

AirSpringFluid

Modern air brake systems are three different systems combined together. They are the service, parking, and the*

S-camFootEmergency

The stop light switch*

Tells you when the air brake system is low on air pressureTurns on the brake lights to warn divers behind youTells you when to use your emergency brakes

If your truck has a dual air brake system and one of the systems is low on pressure:*

The manual slack adjusters on the S-cam brakes are not set properlyEither the front or rear brakes will not be fully operationalThe brake drums will not be fully pressurized

The braking power of the spring brakes:*

Is not affected by the condition of the service brakesCan only be tested by highly-trained brake service peopleDepends on the service brakes being in adjustment

The application pressure gauge shows how much air pressure you:*

Are applying to the brakesHave in the air tanksHave in the modulating control valve

Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least _____ psi*

80100120

If your truck or bus has dual parking control valves, you can use pressure from a separate tank to*

Release the spring emergency/parking brakes to move a short distanceBalance the service brake system when you are parkingStay parked twice as long without using up service air pressure

The brake pedal in an air brake system*

Connects the slack adjusters by a series of rods and linkagesControls the speed of the air compressorControls the air pressure applied to put on the brakes

What is the first thing you should do when a low air pressure warning comes*

Adjust the brake pedal for more travelStop and safely park the truck as soon as possibleOpen the air supply control valve

The S-cam*

Forces the brake shoes against the brake drumsControls time flow of air into the chambersPulls the brake shoes away from the drums and allows the vehicle to roll freely

When is it okay to leave your truck unattended without applying the parking brake or chocking the wheels?*

If you are only gone for a few minutesIf you are conducting a pretrip inspectionNever

In air brake vehicles, the parking brakes should be used*

Any time the vehicle is parkedTo hold your speed when going downhillAs little as possible

The modulating control valve allows you to control the*

Front brakesAmount of air pressure in the brake systemSpring brakes

The brake system that applies and releases the brakes when the driver uses the brake pedal is the ______ brake system.*

ServiceEmergencyParking

Some air brake systems have an alcohol evaporator. What may happen if you don't keep the unit filled with alcohol?*

Ice may form on the brake drums and warp themThe S-cam may not rotate back when you release the brake pedalIce may form in the air storage tanks and cause the brakes to fail

Under normal conditions, to engage the parking brake the driver must first*

Be sure that the air brake system is fully pressurizedTurn off the engineLet the air out of the spring brakes

During normal driving, spring brakes are usually held back by*

Air pressureSpring pressureBolts

If your vehicle has an alcohol evaporator, every day during cold weather you should*

Check the oil for alcohol contentCheck and fill alcohol levelChange the alcohol from a new bottle

The most common type of foundation brake found on heavy vehicles is the*

Disc brakeWedge drumS-cam drum

A supply pressure gauge tells you how much pressure is in the*

Tractor brake linesAir tanksTrailer brake lines

The air compressor governor controls*

When air is pumped into the air storage tanksThe speed of the air compressorAir pressure applied to the brake

It is not safe to drive a vehicle that has brake drums (or discs) with cracks or that are thinner than the manufacturers specifications. Generally this will be ____ of an inch*

1/21/31/4

Your truck or bus has a dual air brake system. If a low air pressure warning comes on for only one system, what should you do?*

Stop and safely park. Continue only after the system is fixedReduce your speed and test the remaining system while drivingReduce you speed and drive to the nearest garage for repairs

Your truck has a properly functioning dual air brake system and minimum size air tanks. The air pressure should build from 85 to 100 psi within ________ seconds

604530

If the spring brakes are on, when should you push the brake pedal?*

NeverOnly when driving down a hillOnly on a slippery road

A truck with air brakes going 55 mph would require a stopping distance of*

100-300 feetMore than 300 feetLess than 100 feet

The spring brakes used on tractors and straight trucks will bring your truck to a stop when the air pressure drops below*

100 psi60 psi20 psi

The air brake lag distance at 55 mph on dry pavement adds about ____ feet to your stopping distance.*

123252

Excessive heat in the brakes can cause the*

Brakes to fade or failModulating control valve to wear outBrake lines to plug

You are on a steep downgrade and have reached your "safe" speed of 40 mph. You would apply the service brakes until your speed drops to ______ mph*

353025

Air braking takes more time than hydraulic braking because air*

Brakes use different brake drumsBrakes require heavier return springsTakes more time to flow through the lines than hydraulic fluid

Total stopping distance for vehicles with air brakes is longer than that for vehicles with hydraulic brakes due to ___________ distance.*

Effective brakingBrake lagReaction

The use of air brakes on a downgrade is only a supplement to the*

Braking effect of the engineUse of the spring brakesUse of the front brake limiting valve

The proper method of braking when going down long and/or steep grades after selecting the proper gear, is to brake until your speed is about ____ mph below your "safe" speed, then to release your brakes*

15105

Which of these is not a proper time to apply the parking brakes?*

When you will only be stopped for less than one hourWhen your brakes are very hotWhen you are going to test the parking brake

You should know your brakes are fading when*

You have to press the brake pedal harder to control the speed on a downgradeThe brake pedal feels "spongy" when you apply pressureYour speed increases when you reduce pressure on your brake pedal

What is emergency stab braking?*

Use light steady pressure on the brake pedalBrake hard, release the brakes when the wheels lock, and reapply the brakes when the wheels start rollingPress hard on the brake pedal and apply full hand valve until you stop

The most important thing to do when a low air pressure warning comes on is*

DownshiftUpshiftStop and safely park as soon as possibte

If you must make an emergency stop, brake so you*

Can steer and your vehicle stays in a straight lineUse the hand brake before the brake pedalUse the full power of the brakes to lock them

Repeatedly pressing and releasing (fanning) the brake pedal may result in*

No change in brake air pressureA build up of brake air pressureThe loss of brake air pressure

Emergency controlled braking is when you*

Apply the hand valve for 1 second, then push hard on the brake pedalApply the brakes as hard as you can without locking up the wheelsBrake as hard as you can, release the brakes when the wheels lock, and put the brakes back on again when the wheels start rolling

An air brake system is fully charged at ____ psi*

12575100

If a tractor or bus has antilock brakes, it will have a _______ ABS malfunction lamp on instrument panel*

RedGreenYellow

Which of the following about antilock braking systems is true?*

ABS won't help you avoid skids caused by over brakingABS allows you to drive faster, follow more closely, and drive less carefullyABS changes the way you brake in emergencies

If your truck's air compressor has its own oil supply, when should you first check the oil level?*

Immediately after you stop drivingBefore drivingDuring your first en route inspection

A slack adjuster probably needs to be adjusted if it moves more than about _____ inch when you pull hard on it*

1/211/4

Excessive use of the service brakes results in overheating, which can lead to:*

Improper adjustment of the S-camIncreased contact between the brake drums and brake liningsExpansion of the brake drums

To check the free play of manual slack adjusters on S-cam brakes, you should park on:*

Level ground, chock the wheels, and turn off the parking brakesLevel ground and drain off air pressure before adjusting vehicle movementLevel ground with the parking brake, then apply the service brake

This is the study material for the Air Brakes test. Please study it until you are comfortable with the material, and then proceed to the practice tests.

ASD Air Brakes Study Material