CLP Air Brake Systems 4

Question 1

What is the purpose of the tractor protection valve?

Accepted Answer

To protect the tractor's air supply if the trailer develops a large air leak or breaks away

Answer

To prevent the driver from applying trailer brakes without applying tractor brakes first

Answer

To regulate the pressure difference between primary and secondary air systems

Answer

To lock the fifth wheel automatically if trailer air pressure drops

Question 2

What is the 'applied stroke' of a brake chamber, and why does it matter?

Accepted Answer

The distance the push rod travels when brakes are fully applied; must stay within legal limits to ensure effective braking

Answer

The total length of the push rod when fully retracted; determines brake chamber size selection

Answer

The speed at which brakes are applied during an emergency stop

Answer

The pressure required to begin moving the push rod from its rest position

Question 3

What does the yellow diamond-shaped control in the cab control?

Accepted Answer

The tractor parking and spring brakes

Answer

The trailer air supply and emergency brakes

Answer

The engine compression brake (jake brake)

Answer

The air dryer heating element in winter

Question 4

During a pre-trip inspection, what is the minimum air pressure you should have before driving a vehicle with air brakes?

Accepted Answer

100 psi

Answer

60 psi

Answer

80 psi

Answer

125 psi

Question 5

What is the proper way to check for air leaks in the brake system during a pre-trip inspection?

Accepted Answer

Build air to operating pressure, shut off engine, apply brakes, and watch pressure gauge for excessive drop

Answer

Listen for hissing while the compressor runs and note any pressure drop

Answer

Drive at 5 mph and apply brakes firmly; leaks will be audible through the floor

Answer

Use soapy water on all fittings while an assistant holds the foot valve down

Question 6

What causes 'compressor knock' or excessive compressor cycling, and what does it indicate?

Accepted Answer

A significant air leak in the system causing the compressor to work overtime to maintain pressure

Answer

Normal operation when traveling at highway speeds with frequent braking

Answer

The air dryer filter needing replacement after extended use

Answer

The governor being set too high, requiring recalibration

Question 7

What is 'rollback' in the context of spring brakes, and how can it be prevented?

Accepted Answer

Backward vehicle movement when releasing the parking brake on a hill before applying the service brake; prevented by coordinating brake and throttle

Answer

The trailer swinging backward when parking; prevented by using wheel chocks

Answer

Air pressure decreasing when going from flat ground to an incline; corrected automatically by the governor

Answer

The push rod retracting too slowly after brake release; corrected by adjusting the slack adjuster