Red Seal Truck and Transport Mechanic Practice Exam

Overheating in a truck engine is often caused by low coolant levels. The coolant is crucial for regulating the engine's temperature, as it absorbs heat and prevents the engine from reaching excessive temperatures. When the coolant level is low, there isn't enough fluid to circulate and effectively carry heat away from the engine. This lack of effective heat dissipation can lead to overheating, which may cause severe damage to engine components such as the head gasket, cylinder heads, and even the engine block itself.

In contrast, while excess oil levels, faulty spark plugs, and high fuel pressure can cause various engine performance issues, they are not direct causes of overheating. Excess oil can actually help in lubrication but may create foaming issues that affect oil pressure. Faulty spark plugs generally affect ignition and combustion efficiency, and while high fuel pressure can lead to poor combustion and engine performance, it does not inherently cause the engine to overheat like a lack of coolant does.