* Low Coolant: The most common cause. If the coolant level is low, the engine can't dissipate heat effectively, leading to overheating. The low coolant could be due to a leak, a faulty radiator cap, or simply not enough coolant in the system.
* Coolant Leak: A leak in the radiator, hoses, water pump, or engine block will cause coolant loss, resulting in overheating and engine shutdown.
* Faulty Water Pump: The water pump circulates coolant through the engine. If it fails, coolant flow stops, leading to overheating.
* Faulty Thermostat: A stuck closed thermostat prevents coolant from circulating until it reaches a certain temperature. This can lead to overheating, especially in situations where the engine is working hard. Conversely, a thermostat that's stuck open might allow the engine to cool too much, but doesn't directly lead to automatic shutoff in most cars.
* Radiator Fan Malfunction: The radiator fan helps cool the coolant. If it fails to turn on when needed, the engine can overheat.
* Clogged Radiator: A radiator clogged with debris restricts coolant flow, hindering heat dissipation.
* Head Gasket Failure: A blown head gasket allows coolant to leak into the engine cylinders or vice versa, leading to overheating and often other serious symptoms like white smoke from the exhaust or loss of compression. This is a serious issue.
* Blocked Cooling System: Something might be obstructing the flow of coolant within the system.
* Sensor Failure: An over-temperature sensor might not be registering the correct temperature, but this is less common as the cause of an immediate shutoff; usually, a warning light will come on first.
* Engine Control Module (ECM) Protection: The car's computer (ECM) monitors engine temperature. When it detects dangerously high temperatures, it'll shut the engine down as a safety precaution to prevent further damage.
In short: The engine shuts off to prevent further damage that would likely be costly to repair. Do *not* restart the engine immediately after it shuts off due to overheating. Let the engine cool completely before attempting to diagnose the issue. Ignoring an overheating problem can lead to severely damaged or destroyed engine components (like cracked cylinder heads or warped engine blocks).
