UK PCV Theory Braking Systems and Technique Questions and Answers Flashcards

You are driving a coach down a long, steep hill. To control your speed and prevent the service brakes from overheating, what is the most effective technique?

Answer: Select a low gear and make use of the engine brake or retarder.

Using a low gear allows the engine's natural resistance (engine braking) to help control the vehicle's speed. This effect is enhanced by an auxiliary braking system like an engine brake or retarder. This technique prevents the service brakes (footbrake) from overheating and losing effectiveness, a dangerous condition known as 'brake fade'.

What is the primary purpose of an Anti-Lock Braking System (ABS) on a PCV?

Answer: To allow the driver to maintain steering control during emergency braking.

The main function of ABS is to prevent the wheels from locking up during heavy braking. By preventing the wheels from skidding, it allows the driver to maintain steering control, which is crucial for avoiding a hazard. While ABS can sometimes reduce stopping distances on good surfaces, its primary safety benefit is the retention of steering control.

Which of the following describes how an exhaust brake works to slow a vehicle?

Answer: It restricts the flow of gases leaving the engine's cylinders.

An exhaust brake is a valve that closes the exhaust path, creating back-pressure in the exhaust manifold and cylinders. This increased pressure makes it harder for the pistons to push exhaust gases out, which slows the engine's rotation and, in turn, slows the vehicle.

A warning light on your dashboard indicates low air pressure in the braking system. You have stopped the vehicle safely. What is the most appropriate action to take?

Answer: Secure the vehicle with the parking brake and investigate the cause, seeking assistance if necessary.

Low air pressure is a critical safety defect in an air brake system, as it can lead to total brake failure. The driver must not continue the journey. The correct procedure is to ensure the vehicle is safely parked (using the parking brake), investigate the cause (such as a leak), and call for technical assistance. Driving a vehicle with known critical brake defects is illegal and dangerous.

The term 'brake fade' refers to a reduction in braking efficiency. What is the most common cause of this phenomenon?

Answer: Excessive heat build-up in the braking components from prolonged use.

Brake fade is the loss of braking power that occurs when the braking system overheats. This typically happens during long descents or repeated heavy braking. The high temperatures can cause the brake pads to lose their frictional properties and can even boil the brake fluid, making the brakes feel spongy and ineffective.

During your daily walk-around check, which of the following is a key inspection related to the air braking system?

Answer: Listening for any audible air leaks from pipes and reservoirs.

The daily walk-around check is a legal requirement to ensure the vehicle is roadworthy. For a vehicle with air brakes, listening for audible leaks is a critical check. An air leak could lead to a loss of braking pressure while on the road, creating a significant safety risk.