CPC Vehicle Systems 2

Question 1

What is a retarder and what types are used on HGVs?

Accepted Answer

An auxiliary braking device — types include exhaust brakes, engine brakes (Jake brakes), and electromagnetic retarders

Answer

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)?

Accepted Answer

To trap and periodically burn off soot particles from the exhaust, reducing particulate emissions

Answer

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?

Accepted Answer

To provide a smoother ride, protect the load, allow ride height adjustment, and distribute weight more evenly

Answer

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?

Accepted Answer

The coupling device on the tractor unit that connects to and supports the front of the semi-trailer

Answer

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?

Accepted Answer

Low coolant can cause the engine to overheat, potentially causing catastrophic engine damage

Answer

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.

UK Driver CPC Practice Test

UK Driver CPC Practice Test

CPC Vehicle Systems 2