Overheating occurs when heat production exceeds heat dissipation. Internal combustion engines rely on coolant, fans, sensors, and pump pressure.
1. Low Coolant (Most Common Case)
Coolant absorbs heat from the engine block.
Facts
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Coolant must be a 50/50 ethylene glycol and water mix
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Low coolant reduces heat transfer capacity by up to 40%
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Air pockets cause localized hotspots
2. Thermostat Failure
The thermostat controls coolant flow.
If Stuck Closed:
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Coolant cannot reach radiator
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Engine overheats rapidly
If Stuck Open:
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Engine runs too cold
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Poor fuel economy
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Long-term wear increases
3. Radiator Blockage
Radiators get clogged internally (rust, debris) or externally (dirt, leaves).
Measured Impact
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A 30% blockage increases temperature by 10–15°C
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Coolant flow restriction causes boiling
4. Water Pump Failure
The water pump circulates coolant.
Signs
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Coolant leaks from pump seal
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Grinding noise
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Overheating at idle
Facts
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Pumps fail between 150,000–200,000 km
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Impellers sometimes corrode (Volkswagen/Audi common issue)
5. Cooling Fan Failure
Fans maintain airflow when stationary or slow-moving.
Common Failures
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Burnt fan motor
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Faulty relay
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Blown fuse
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Bad temperature sensor
6. Head Gasket Failure
A blown head gasket causes coolant to enter cylinders.
Evidence
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White smoke
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Bubbles in the radiator
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Coolant loss with no visible leak
Conclusion
Overheating is nearly always caused by coolant loss, pump failure, radiator blockage, thermostat malfunction, or fan issues.
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