Car Overheating: Causes & Fixes
Reviewed by the Wrenchit.ai editorial team · Last reviewed · Editorial standards
Causes ranked by likelihood
| Cause | Likelihood |
|---|---|
| Low coolant (leak) — Look for green, orange, or pink puddles. Common leak points: radiator, hoses, water pump weep hole, heater core. | Most likely |
| Stuck-closed thermostat — Engine heats up fast at idle but the upper radiator hose stays cold. Cheap part, easy DIY on most cars. | Possible |
| Failed radiator fan or fan relay — Overheats in traffic and at idle but cools down at highway speed. Listen for the fan kicking on around 220°F. | Possible |
| Failed water pump — Often leaks coolant from a weep hole behind the timing cover. May whine or wobble. | Less likely |
| Blown head gasket — White exhaust smoke, milky oil, bubbles in the coolant reservoir, or coolant loss with no visible leak. | Less likely |
How to narrow it down
- Note when it happens. Record speed, temperature, and whether braking, turning or accelerating triggers it.
- Scan for codes. Plug in an OBD-II scanner — a stored code narrows the cause quickly.
- Check: Low coolant (leak). Look for green, orange, or pink puddles. Common leak points: radiator, hoses, water pump weep hole, heater core.
- Check: Stuck-closed thermostat. Engine heats up fast at idle but the upper radiator hose stays cold. Cheap part, easy DIY on most cars.
- Check: Failed radiator fan or fan relay. Overheats in traffic and at idle but cools down at highway speed. Listen for the fan kicking on around 220°F.
- Check: Failed water pump. Often leaks coolant from a weep hole behind the timing cover. May whine or wobble.
- Check: Blown head gasket. White exhaust smoke, milky oil, bubbles in the coolant reservoir, or coolant loss with no visible leak.