Montana CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

The manual's standard for a dual air system is 45 seconds to climb from 85 psi to 100 psi at operating rpm. When does it say a longer time can still be safe?

Accepted Answer

When the vehicle has air tanks larger than the minimum size — The manual says a vehicle with larger-than-minimum air tanks can take longer to build pressure without being unsafe, and it tells you to check the manufacturer's specifications.

Answer

When the outside temperature is below freezing

Answer

When the vehicle is fully loaded

Answer

When the alcohol evaporator is empty

Question 2

Which problem does the manual say roadside inspections turn up more often than any other?

Accepted Answer

Brakes that are out of adjustment — The manual names out-of-adjustment brakes as the most common problem found at roadside inspections, which is why it stresses checking the slack adjusters.

Answer

Air tanks that have not been drained

Answer

Low alcohol level in the evaporator

Answer

Burned-out ABS malfunction lamps

Question 3

During the emergency brake test on the vehicle inspection test, you are fanning off air in a vehicle whose valves are not the pop-out kind. How does the manual say you will know the parking or emergency brakes have applied?

Accepted Answer

By listening for air discharging from the air system — Normally the parking brake valve should close, or pop out, between 20 and 45 psi or at the manufacturer's level. Where the valves do not pop out, the manual says the sound of air being discharged tells you the brakes have applied.

Answer

By watching for the ABS lamp to flash

Answer

By feeling the brake pedal go to the floor

Answer

By waiting until the gauge reads zero

Question 4

You are building air pressure in a dual system before a trip. At what point does the manual say the low air warning light and buzzer should go off?

Accepted Answer

When both systems reach a manufacturer-set value that is above 55 psi — The manual says the warning should shut off once pressure in both systems climbs to a level the manufacturer sets, and that level has to be more than 55 psi. Separately, it tells you to let both systems build to at least 100 psi before you drive.

Answer

As soon as either system passes 20 psi

Answer

Only when both systems reach governor cut-out

Answer

When the primary system alone reaches 100 psi

Question 5

In a wedge brake, what does the brake chamber push rod do?

Accepted Answer

It drives a wedge straight in between the ends of the brake shoes — The manual says the push rod in a wedge brake forces a wedge in between the shoe ends, spreading the shoes against the inside of the drum. A twisting camshaft belongs to s-cam brakes and a power screw to disc brakes.

Answer

It twists a camshaft that turns an S-shaped cam

Answer

It turns a power screw that clamps a rotor

Answer

It pulls the slack adjuster toward the brake chamber

Question 6

You pull hard on a slack adjuster during the walk-around and it travels roughly an inch and a half at the point where the push rod attaches. What does the manual say about that brake?

Accepted Answer

It probably needs adjustment — The manual's rule of thumb is about one inch of movement at the push rod. More than that and the brake probably needs adjusting, and the manual warns that excess slack can make a vehicle very difficult to stop.

Answer

It is within limits; up to two inches of travel is acceptable

Answer

It shows the automatic drain valve has failed

Answer

It means the spring brake is still applied

Question 7

It is January and your truck has an alcohol evaporator and manually drained air tanks. A coworker says the evaporator means you can skip draining the tanks. What does the manual say?

Accepted Answer

He is wrong; the tanks still need draining every day to remove water and oil — The evaporator feeds alcohol into the air system to cut the risk of ice forming in valves and other parts. The manual adds that the tanks must still be drained daily to remove water and oil. The only exception is a system whose drain valves are automatic.

Answer

He is right; alcohol dissolves the water and oil in the tanks

Answer

He is right, but only while the temperature stays below freezing

Answer

He is wrong; with an evaporator the tanks must be drained after every stop

Question 8

Before checking slack adjusters on s-cam brakes, the manual has you chock the wheels on level ground and then release the parking brakes. Why release them?

Accepted Answer

So that the slack adjusters can be moved by hand — The manual says releasing the parking brakes is what lets you move the slack adjusters. The chocks are there to keep the vehicle from rolling while the brakes are off.

Answer

So that the air tanks drain while you work

Answer

So that the low air warning can be tested at the same time

Answer

So that the brake drums cool faster

Question 9

In the air leakage rate test on the vehicle inspection test, you shut off the engine, release the brakes and press the foot brake all the way down. When does the manual's one-minute count begin?

Accepted Answer

After the gauge needle settles following the first drop caused by the brake application — Applying the foot brake causes an initial drop on the gauge. The inspection section says to wait for the gauge to stabilize, then hold the pedal for one minute and look for a loss of no more than 3 pounds on a single vehicle or 4 pounds on a combination.

Answer

The moment the engine is shut off

Answer

When the low air warning comes on

Answer

After the parking brake valve pops out

Question 10

Your test vehicle has primary and secondary air brake systems. For the emergency brake test, what does the manual's inspection section say you must explain to the examiner?

Accepted Answer

That there is a backup system, so the valves will not pop out when only one system loses pressure — With two systems, losing pressure in just one of them does not make the parking brake valve close. The inspection section expects you to explain that backup arrangement and to know the manufacturer's specifications for the vehicle you bring to the test.

Answer

That the secondary system is used only for the trailer

Answer

That the valves pop out as soon as either system falls below 100 psi

Answer

That dual systems are exempt from the emergency brake test

Question 11

Some of the brakes on your vehicle are out of adjustment while the rest are adjusted correctly. What does the manual say happens as you keep braking?

Accepted Answer

The out-of-adjustment brakes quit doing their share first, and the others can then overheat and fade — The manual says safe control requires every brake to carry its part of the load. Brakes that are out of adjustment drop out early, the remaining brakes take the extra heat and fade, and there may not be enough braking left to control the vehicle.

Answer

The out-of-adjustment brakes lock up while the others release

Answer

All of the brakes share the load evenly anyway

Answer

The spring brakes take over for the out-of-adjustment brakes

Question 12

Every vehicle built since 1994 has automatic slack adjusters. According to the manual, when do they adjust themselves?

Accepted Answer

During full brake applications — Automatic slack adjusters take up slack on their own when the brakes are fully applied. The manual says they still have to be checked.

Answer

Each time the governor cuts in

Answer

Whenever the parking brake is set

Answer

Only while the vehicle is backing up

Montana CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. The manual's standard for a dual air system is 45 seconds to climb from 85 psi to 100 psi at operating rpm. When does it say a longer time can still be safe?

2. Which problem does the manual say roadside inspections turn up more often than any other?

3. During the emergency brake test on the vehicle inspection test, you are fanning off air in a vehicle whose valves are not the pop-out kind. How does the manual say you will know the parking or emergency brakes have applied?

4. You are building air pressure in a dual system before a trip. At what point does the manual say the low air warning light and buzzer should go off?

5. In a wedge brake, what does the brake chamber push rod do?

6. You pull hard on a slack adjuster during the walk-around and it travels roughly an inch and a half at the point where the push rod attaches. What does the manual say about that brake?

7. It is January and your truck has an alcohol evaporator and manually drained air tanks. A coworker says the evaporator means you can skip draining the tanks. What does the manual say?

8. Before checking slack adjusters on s-cam brakes, the manual has you chock the wheels on level ground and then release the parking brakes. Why release them?

9. In the air leakage rate test on the vehicle inspection test, you shut off the engine, release the brakes and press the foot brake all the way down. When does the manual's one-minute count begin?

10. Your test vehicle has primary and secondary air brake systems. For the emergency brake test, what does the manual's inspection section say you must explain to the examiner?

11. Some of the brakes on your vehicle are out of adjustment while the rest are adjusted correctly. What does the manual say happens as you keep braking?

12. Every vehicle built since 1994 has automatic slack adjusters. According to the manual, when do they adjust themselves?

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