Fuel, Lubrication and Cooling Systems
Domain focus
Fuel, Lubrication and Cooling Systems tests how fuel is delivered, how friction is controlled, and how engine temperature is regulated. Expect pump, filter, injector, oil, coolant, thermostat, and radiator questions.
Core rules
- Petrol engines may use carburettor, MPFI, or direct injection; diesel engines use high-pressure injection. The fuel filter traps dirt and water; injectors atomise fuel.
- Lubrication reduces friction, cools, cleans, and seals. The oil pump draws oil from the sump through a strainer and filter; viscosity must match the recommended grade and climate.
- Cooling uses coolant circulation, radiator, thermostat, water pump, and fan. The thermostat opens as coolant warms to regulate temperature.
- Never open a hot radiator cap; allow cooling and use the correct coolant mix.
Worked example
An engine overheats and the coolant level is normal, but the upper hose stays cold and the fan runs. A stuck-closed thermostat is likely: coolant cannot circulate to the radiator. The reasoning is that a cold upper hose with high engine temperature points to no flow, not a fan fault. Test or replace the thermostat to specification.
Traps
Using the wrong oil grade, overfilling oil, ignoring a coolant leak, and misfuelling petrol and diesel are common mark losers.