UK PCV Theory Braking Systems and Technique Questions and Answers — Questions and Answers
Question 1: 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?
- Select a low gear and make use of the engine brake or retarder. (Correct answer)
- Ride the footbrake lightly to maintain a constant speed.
- Apply the parking brake intermittently to assist the service brakes.
- Select a high gear to allow the engine to run freely.
Correct 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'.
Question 2: What is the primary purpose of an Anti-Lock Braking System (ABS) on a PCV?
- To reduce the overall stopping distance in all weather conditions.
- To allow the driver to maintain steering control during emergency braking. (Correct answer)
- To automatically apply the brakes if a hazard is detected.
- To prevent the service brakes from wearing out prematurely.
Correct 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.
Question 3: Which of the following describes how an exhaust brake works to slow a vehicle?
- It uses electromagnetic resistance on the driveshaft.
- It reverses the flow of hydraulic fluid in the transmission.
- It restricts the flow of gases leaving the engine's cylinders. (Correct answer)
- It applies light pressure to the service brakes automatically.
Correct 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.
Question 4: 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?
- Continue the journey at a reduced speed, braking gently.
- Pump the brake pedal several times to try and build up pressure.
- Secure the vehicle with the parking brake and investigate the cause, seeking assistance if necessary. (Correct answer)
- Switch the engine off and on again to see if the warning light resets.
Correct 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.
Question 5: The term 'brake fade' refers to a reduction in braking efficiency. What is the most common cause of this phenomenon?
- The brake fluid becoming too cold in winter weather.
- Excessive heat build-up in the braking components from prolonged use. (Correct answer)
- Moisture getting onto the brake discs during wet weather.
- A fault within the Anti-Lock Braking System (ABS) computer.
Correct 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.
Question 6: During your daily walk-around check, which of the following is a key inspection related to the air braking system?
- Checking that the tyre pressures are correct for the load.
- Listening for any audible air leaks from pipes and reservoirs. (Correct answer)
- Ensuring the steering wheel has no excessive play.
- Confirming that all passenger seatbelts are in good working order.
Correct 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.
UK PCV Theory Braking Systems and Technique Questions and Answers
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?