CDL AIR BREAK 71 QUESTION

The application pressure gauge shows

how much air pressure you:

are applying to the breaks

The spring brakes used on the chambers

in a straight truck will bring you to a stop

when air pressure drops below

psi.

20

Some air brake systems have an alcohol

evaporator. What may happen if you don't

keep the proper level of alcohol?

Ice may form in the air brake valves and

cause brake failure.

Your truck or bus has a dual air brake

system. If a low-pressure warning comes

on for only one system, what should you

do?

Bring your vehicle to a complete stop

right away and safely park. Continue

only after the system is fixed.

Why drain water from compressed air

tanks?

water may freeze in cold weather and cause brake failure

The safety valve is set automatically when

pressure iS;

150

Your truck has a dual air system and one

of the systems loses its pressure. What

will happen?

Either the front or back brake will not be

fully operational.

Parking or emergency brakes of trucks

and buses can be legally held on by

pressure.

spring

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 distance.

If your truck has a properly functioning

dual air brake system and minimum size

air tanks, the air pressure should build up

from 85 to 100 psi within how many

seconds?

45

How should you check that your service

brakes are working properly?

Park on level ground, wait until normal

air pressure is reached, release the

parking brake and move forward slowly

at about 5 mph. Then apply the brakes

firmly.

A straight truck or bus air brake system

should not leak at the rate of more than

psi per minute with the engine off

and the brakes released.

2

During normal driving, spring brakes are

usually held back by:

air pressure

The air compressor stops pumping air at

what psi?

125 psi

The driver must be able to see a low air

pressure warning which comes on before

pressure in the service air tanks fall below

psi.

60 psi

Excessive use of the service brakes

results in overheating which can lead to:

Expansion of the break drums.

The most common type of foundation

brake found on heavy vehicles is the:

S-cam drum brake

If you must make an emergency stop, you

should brake so you:

Can keep your vehicle in a straight line.

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 right away and safely park.

Continue only after the system is fixed.

If your vehicle has an alcohol evaporator,

every day during cold weather you

should:

Check and fill the alcohol level.

The air loss rate for a straight truck or bus

with the engine off and the brakes on

should not be more than:

3 psi in 1 minute

The driver must be able to see a low air

pressure warning which comes on before

pressure in the service air tanks falls

below

psi.

60

.

The air brake lag distance at 55 mph on

dry pavement adds about

feet.

32 feet

Total stopping distance for air brakes is

longer than that for hydraulic brakes due

to

distance.

Brake lag

It is accepted that too much heat caused

by using your brakes too often can also

cause:

Brake to fade or fail

Repeatedly partially increasing and

pressing the brake pedal may result in:

A loss of air brake pressure

The brake system that applies and

releases the brakes when the driver uses

the brake pedal is the

brake

system.

service

A slack adjuster's free play needs to be

adjusted if it is more than about

when you pull hard on it.

1 inch

An air brake system is fully charged at

what psi?

125 psi

The brake pedal in an air brake system:

Controls the air pressure applied to the brakes

The S-cam:

Forces the brake shoes against the

inside of the brake drum.

Under normal conditions, in order to

engage the parking brakes the driver

should:

Apply brakes by pulling the parking

brake control knob out.

All air brake equipped vehicles have:

A supply pressure gauge

With air brake vehicles, the parking brake

should be used:

Whenever you leave the vehicle unattended

If the air compressor should develop a

leak, what keeps the air in the tanks?

The one-way check valve.

Which of these is NOT a proper time to

apply the parking brakes?

If the brakes are very hot (e.g. Just after

coming down a steep grade).

With air brake vehicles, the parking

brakes should be used:

Any time when vehicle is parked

Why should you drain water from

compressed air tanks?

Water can freeze in cold weather and

cause brake failure.

If the spring brakes are on, when should

you push the brake pedal?

never

To check the free play of manual slack

adjusters of S-cam brakes, you should

park on:

Level ground, chock the wheels and

release the parking brakes.

Excessive heat caused by using your

brakes too often can also cause:

Brake to fade or fail

If you must make an emergency stop, you

should brake so you:

Can steer and so your vehicle stays in a straight line

The use of brakes on a long and steep

downgrade under normal conditions is

only a supplement to:

Braking effect of the engine

The most important thing to do when a

low air pressure warning comes on is:

Stop and safely park as soon as possible

The parking or emergency brake on a

heavy vehicle can only be held in position

by something that cannot leak away, like:

Spring pressure

Air braking takes more time than hydraulic

braking because:

Air brakes take more time to flow

through the lines than hydraulic fluid.

When brakes are applied, the brake shoes

will press against the:

Brake drum or disc

The safety valve discharges automatically

at the pressure of:

150 psi

Emergency stab braking is:

Press on the brake pedal as hard as you

can, release the brakes when the

wheels lock, put on the brakes again

when the wheels start rolling.

If air pressure is not built up within the

correct amount of time, then:

Air pressure may drop to a low point

while driving, requiring an emergency

stop.

The safety valve reduces pressure at

psi.

150

What can legally hold a parking or

emergency brake in position for a truck,

truck tractor, or bus?

Spring pressure

The supply pressure gauge shows how

much pressure:

Is in the air tanks

The braking power of the spring brakes:

Depends on the brakes being in

adjustment.

It is not safe to drive a vehicle that has

brake drums with cracks that are longer

than

of the width of the friction

area.

1/2

Your brakes are fading when:

You have to push harder on a brake

pedal to control your speed on a

downgrade.

If your vehicle has an alcohol evaporator,

it is there to:

Reduce the risk of icing in air brake

valves in cold weather.

The air compressor governor controls:

When air is pumped into the air tanks.

Modern air brakes combine three different

systems. They are the service, the

parking, and the

brakes.

Emergency

If you do not have automatic tank drains,

how often should you drain the oil and

water from the bottom of compressed air

storage tanks?

At the end of each day of driving

The proper use of the brakes when going

down a long steep grade after selecting a

proper gear is to brake until your speed is

about

below the posted speed and

release your brake.

5 mph

In ideal conditions a truck or bus with air

brakes going at 55 mph would require the

stopping distance of how many feet?

More than 300 feet

When is it Ok to leave your truck

unattended without applying the parking

brakes and choking the wheels?

never

The stop light switch:

Turns on the brake lights when you put

on the air brakes.

The shows how much pressure is in the air tanks

supply pressure gauge

To test air service brakes you should:

Brake firmly while slowly moving

forward.

If you are driving down a steep

downgrade and have reached your safe

speed of 40 mph, you would apply the

service brake until your speed dropped to

mph,

35

If your truck has a dual air brake system,

and one of the systems is low on

pressure:

Either the front or rear brakes will not be

fully functional.

What happens when your brake drums

get very hot?

they expand

What is a "Wig Wag"

A mechanical arm that signals low air

pressure.