If your vehicle is showing engine overheating warning light illuminated, here are the most likely causes and the parts you'll need to fix each one.
The most frequent cause of overheating is simply a lack of coolant due to a leak in an aging hose, the radiator, or the plastic overflow tank.
The thermostat regulates coolant flow to the radiator. If it fails and sticks in the closed position, hot coolant is trapped inside the engine block.
If the electric cooling fan fails to turn on, no air is pulled through the radiator at low speeds or when idling, causing temperatures to spike in traffic.
The water pump circulates coolant through the engine. If its internal impeller degrades or the bearing fails, coolant stops flowing and the engine overheats rapidly.
On many vehicles, the drive belt powers the water pump. If the belt snaps, the water pump stops turning immediately, often accompanied by a loss of power steering and alternator charging.
If the cooling system was recently flushed or parts were replaced without properly bleeding the system, trapped air pockets will block coolant flow and cause rapid overheating.
Sometimes the engine isn't actually overheating, but a failing sensor sends a false high-temperature reading to the dashboard, triggering the warning light.
A catastrophic failure where the gasket sealing the engine block and cylinder head ruptures, allowing superheated combustion gases to enter the cooling system.