CPC Vehicle Systems 2 — Questions and Answers
Question 1: What is a retarder and what types are used on HGVs?
- A speed limiting device
- An auxiliary braking device — types include exhaust brakes, engine brakes (Jake brakes), and electromagnetic retarders (Correct answer)
- A GPS tracking system
- A device to slow trailer loading
Correct answer: An auxiliary braking device — types include exhaust brakes, engine brakes (Jake brakes), and electromagnetic retarders
A retarder is an auxiliary braking system that slows the vehicle without using the service brakes. Types include exhaust brakes (restricting exhaust flow), engine brakes/Jake brakes (using engine compression), and electromagnetic retarders (using magnetic resistance). They preserve service brake life.
Question 2: What is the function of the DPF (Diesel Particulate Filter)?
- To filter the air entering the engine
- To trap and periodically burn off soot particles from the exhaust, reducing particulate emissions (Correct answer)
- To filter diesel fuel before injection
- To reduce engine noise
Correct answer: To trap and periodically burn off soot particles from the exhaust, reducing particulate emissions
The DPF captures soot particles from the exhaust gas and periodically undergoes 'regeneration' where the trapped soot is burned off at high temperature. This dramatically reduces particulate matter emissions. Drivers should allow regeneration to complete and not interrupt it.
Question 3: What is the function of air suspension on an HGV?
- To make the cab more comfortable for the driver only
- To provide a smoother ride, protect the load, allow ride height adjustment, and distribute weight more evenly (Correct answer)
- To increase vehicle speed
- To reduce the need for tyres
Correct answer: To provide a smoother ride, protect the load, allow ride height adjustment, and distribute weight more evenly
Air suspension uses air bags instead of steel springs. Benefits include a smoother ride that protects cargo, the ability to adjust ride height for loading docks, automatic load levelling, and reduced road damage compared to steel suspension.
Question 4: What is the 5th wheel coupling on an articulated HGV?
- A spare wheel mounted on the chassis
- The coupling device on the tractor unit that connects to and supports the front of the semi-trailer (Correct answer)
- The steering wheel
- A wheel on the trailer landing gear
Correct answer: The coupling device on the tractor unit that connects to and supports the front of the semi-trailer
The 5th wheel is a large, greased coupling plate mounted on the tractor unit's chassis. The trailer's kingpin drops into the 5th wheel's jaws, creating a secure but pivoting connection. It carries a significant proportion of the trailer's weight.
Question 5: Why is it important to check the coolant level regularly on an HGV?
- Coolant only affects the heater
- Low coolant can cause the engine to overheat, potentially causing catastrophic engine damage (Correct answer)
- Coolant is purely cosmetic — it colours the radiator fluid
- Coolant levels only matter in winter
Correct answer: Low coolant can cause the engine to overheat, potentially causing catastrophic engine damage
The cooling system prevents the engine from overheating. Low coolant can lead to overheating, which can cause warped cylinder heads, blown head gaskets, seized pistons, or complete engine failure. Coolant also provides frost protection and corrosion inhibition.
Question 6: What does the EBS (Electronic Braking System) provide over standard ABS?
- Louder brake noise for warning pedestrians
- Faster brake response times, automatic load-sensing, and integration with stability control systems (Correct answer)
- A cheaper braking system
- Longer brake pedal travel
Correct answer: Faster brake response times, automatic load-sensing, and integration with stability control systems
EBS provides faster brake response (up to 0.3 seconds faster than pneumatic-only systems), automatic load-proportioning, integration with ESC (Electronic Stability Control), and diagnostic capabilities. It uses electronic signals to control pneumatic brake application.
CPC Vehicle Systems 2
What is a retarder and what types are used on HGVs?