Reasons a Car Will Overheat

A low engine coolant level is a prime cause of car overheating. Engine coolant, which flows throughout a car's engine and picks up heat from the internal engine parts and transports it to the radiator, is responsible for lowering and maintaining engine operating temperatures. A lack of sufficient engine coolant results in increased engine operating temperatures, and can lead to engine overheating if coolant levels are low enough.

A car's thermostat is a small heat-sensitive valve that opens and closes in response to engine temperature. When open, the thermostat allows heated engine coolant to flow into the radiator, where the radiator cools the heated fluid and prepares it for reentry into the engine. In the closed position, the thermostat prevents engine coolant from entering the radiator, which helps speed warm-up of a cold engine. If the thermostat gets stuck in the closed position, engine coolant stays in the engine and quickly becomes overheated, which can lead to engine overheating.

For engine coolant to flow properly throughout a car's engine, the small engine coolant passageways through which coolant flows need to be open and unobstructed. Rust, dirt and grime can all lodge inside these passageways and impede normal coolant flow. The results can be insufficient engine cooling and elevated engine operating temperatures, which can lead to engine overheating if coolant passageways are severely blocked.

To maximize the effectiveness of a radiator, a radiator fan is used to blow air across the radiator fins, which are small passageways within the radiator in which coolant travels and through which the radiator extracts heat from the heated coolant. As the coolant flows through the radiator fins, the radiator fan blows air directly across the fins, which further reduces coolant temperature. A broken radiator fan impedes normal radiator function and results in higher coolant temperatures, which can lead to engine overheating in many instances.

A faulty radiator can cause a car to overheat by preventing the adequate cooling of circulating engine coolant, which ultimately leads to an increase in engine operating temperatures and, in severe cases, engine overheating. As coolant travels through a car's engine, it picks up heat from the internal engine parts and then flows to the radiator, where the heat is extracted from the engine coolant and radiated into the outside air. This allows the engine coolant to pick up additional engine heat as it leaves the radiator and flows back to the engine. Any disruption in radiator function can lead to elevated engine operating temperatures and overheating.