Air Brakes

Question 1

What can cause brakes to fail or fade?

Answer 1

Excessive use of the service brakes, not relying on engine braking enough, and brakes being out of adjustment.

Question 2

Which device helps reduce the risk of ice in the air brake systems during cold weather?

Answer 2

Alcohol evaporator

Question 3

Slack adjusters are:

Answer 3

Between the power screw and push rod on disc brakes, part of your air brake system used to adjust the brakes, and between the push rod and S-cam on drum brakes.

Question 4

What is the correct way to slow a large vehicle down on long downgrades?

Answer 4

Using a low gear and driving more slowly.

Question 5

What should you never do when the spring brakes are on?

Answer 5

Push the brake pedal down.

Question 6

Pressing on the brakes as hard as you can, releasing when they lock up, then pressing the brakes fully again when the wheels are rolling is called what?

Answer 6

Stab braking.

Question 7

If the brakes are wet, what can be done to dry them out?

Answer 7

Use the brakes lightly while driving in low gear.

Question 8

What is a reason that air tanks must be drained?

Answer 8

Your brakes may fail due to the water freezing.

Question 9

Where is compressed air stored?

Answer 9

Main reservoirs

Question 10

Most heavy-duty vehicles have dual air brake systems. What is a dual air brake system?

Answer 10

Two separate air brake systems that use a single set of brakes controls.

Question 11

In a dual air brake system, which parts of braking does each system typically operate?

Answer 11

One system operates the brakes on the rear axle/axles, the other operates the regular brakes on the front axle (and possibly a rear axle). Both supply air to the trailer.

Question 12

Spring brakes are?

Answer 12

Made up of powerful springs that are held in back while you are driving by air pressure, brakes that come on automatically on a truck or tractor when the PSI drops too low, not going to have full effect until your PSI drops to a certain range, often 20 to 30 PSI.

Question 13

When should you not use the parking brakes when parking?

Answer 13

If the brakes are very hot or very wet in freezing temperatures.

Question 14

When ABS fails can you still drive your truck?

Answer 14

Yes, you will still have normal brake function and simply need to get the ABS repaired soon.

Question 15

How do brakes work on a long, steep downgrade?

Answer 15

As a supplement to the braking effect of your engine.

Question 16

How would you check your truck’s slack adjusters?

Answer 16

Use gloves and pull hard on each slack adjusters you can reach.

Question 17

To test the air leakage rate, one must turn off engine(with a fully charged air system), turn the key to the on position, release the service brake, and do what?

Answer 17

Time the air pressure drop.

Question 18

If you press and release the brake pedal rapidly, what will happen?

Answer 18

You can let the air out faster than the compressor can replace it.

Question 19

What is a modulating control valve?

Answer 19

A lever used to apply the spring brakes gradually.

Question 20

Chemical changes in the braking lining, which reduce friction and cause expansion on the brake drums is known as what?

Answer 20

Brake fade

Question 21

Why is it especially important to have your brakes adjusted before going down steep grades?

Answer 21

Some brakes will do more work than others.

Question 22

What is true about a dual air brake system?

Answer 22

One is called the primary system and one is called the secondary system, one system usually operates the front axle and one operates the rear axle, they use a single set of brake controls.

Question 23

With air brakes, there is an added delay when stopping. What causes this?

Answer 23

The time required for the air to flow through the lines to the brakes.

Question 24

If parking brakes are not being used when vehicle is parked, what must be done instead?

Answer 24

Use wheel chocks

Question 25

Which device allows you to remove oil and water from the air brake system?

Answer 25

Air tank drain.

Question 26

Before driving a vehicle with a dual air system, the driver must allow what to happen?

Answer 26

The air compressor to build up a minimum of at least 100 PSI in both the primary and secondary systems

Question 27

What does it mean when the safety valve opens and releases air?

Answer 27

The pressure has exceeded 150 PSI and something is wrong, a mechanic needs to check it.

Question 28

What should you do before leaving your truck unattended?

Answer 28

Chock the wheels, put on the parking brakes, and remove the keys.

Question 29

What is the best way to test if your vehicle’s spring brakes come on automatically?

Answer 29

Continue to step on and off the brake pedal until the parking brake valve pops out, on tractor trailer vehicles.

Continue to step on and off the brake pedal until the manufacturer’s low PSI specification has been met for the spring brakes to deploy.

Continue to step on and off the brake pedal until the parking brake valve pops on single vehicles.

Question 30

When should you drain your air tanks?

Answer 30

At the end of each working day.