A car overheats while driving primarily due to a failure in its cooling system, which is designed to manage the immense heat generated by the engine. The most common culprits are a low coolant level, a malfunctioning thermostat (a valve that regulates coolant flow), a broken water pump, a clogged radiator, or a faulty cooling fan. Ignoring an overheating engine can lead to severe and costly damage, including a warped cylinder head or a blown head gasket.
The cooling system works by circulating a mixture of coolant and water through passages in the engine block. As the coolant absorbs heat, it flows to the radiator, where air passing through cools it down before it recirculates. If any part of this loop fails, heat builds up rapidly.
Here are the most frequent causes and their typical symptoms:
| Cause of Overheating | Common Symptoms | Potential Repair Cost Range (USD) |
|---|
| Low Coolant Level | Coolant leak under car, rising temperature gauge, heater not working | $50 - $200 (for top-up and leak repair) |
| Faulty Thermostat | Engine heats up quickly, temperature gauge fluctuates wildly | $150 - $400 |
| Radiator Issues (clogged or leaking) | Visible coolant leaks from radiator, overheating in traffic | $300 - $1,200 |
| Water Pump Failure | Coolant leak from front of engine, whining noise, steam | $400 - $800 |
| Cooling Fan Failure | Overheating when idling or in slow traffic, fan not turning on | $200 - $600 |
| Blown Head Gasket | White smoke from exhaust, coolant loss with no visible leak, milky oil | $1,500 - $2,500+ |
If your temperature gauge spikes, your first action should be to turn off the air conditioning and turn on the heater to its highest setting and fan speed. This helps draw heat away from the engine. Safely pull over and shut off the engine. Do not open the radiator cap while the engine is hot, as the pressurized system can spray scalding coolant. The best course of action is to call for a tow to a trusted mechanic to diagnose the root cause.
