CLP Air Brake Systems 3

Question 1

What is the correct technique for braking on a long, steep downgrade with air brakes?

Accepted Answer

Apply brakes firmly to reduce speed by about 5 mph, release, then reapply as needed

Answer

The proper technique is to apply brakes firmly until speed drops about 5 mph below your target speed, then release them and allow brakes to cool before reapplying.

Question 2

What does a properly functioning air dryer do in an air brake system?

Accepted Answer

Removes moisture and contaminants from compressed air before it reaches the tanks

Answer

An air dryer removes water vapor and contaminants from compressed air to prevent moisture buildup that could freeze lines or damage system components.

Question 3

How much air pressure loss per minute is acceptable for a combination vehicle during the static leakage test with brakes released?

Accepted Answer

5 psi or less

Answer

For a combination vehicle with brakes released, the air pressure should not drop more than 4 psi in one minute (3 psi for single vehicles); 5 psi or less is acceptable.

Question 4

What is the role of the S-cam in a drum air brake system?

Accepted Answer

It rotates to force the brake shoes outward against the brake drum when brakes are applied

Answer

When air pressure moves the push rod, it turns the S-cam, which pushes the brake shoes outward against the drum to create friction and slow the vehicle.

Question 5

Why should you never push down the brake pedal to release spring brakes (parking brakes) when there is no air pressure?

Accepted Answer

There is no air pressure to compress the springs, so the service brake pedal cannot release them

Answer

Spring brakes are held released by air pressure; without air, the springs are fully extended and the foot valve cannot mechanically compress them.

(CLP) Commercial Learner's Permit Practice Test

(CLP) Commercial Learner's Permit Practice Test

CLP Air Brake Systems 3