Why is my car overheating?
An overheating engine is almost always a coolant problem: low coolant from a leak, a stuck thermostat, a failed water pump, or a bad radiator fan. Stop driving immediately if the temperature gauge enters the red — you can warp the cylinder head ($1,500+) or crack the engine block (totaled engine).
Cost range: $50–$2,500. Severity: high. Safe to drive? No. Pull over, shut off the engine, and let it cool for 30+ minutes before opening the cap. Driving an overheated engine more than a few minutes can destroy it.
Most likely causes
- Low coolant (leak) — Look for green, orange, or pink puddles. Common leak points: radiator, hoses, water pump weep hole, heater core. ($50–$800, common)
- Stuck-closed thermostat — Engine heats up fast at idle but the upper radiator hose stays cold. Cheap part, easy DIY on most cars. ($50–$400, common)
- 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. ($200–$700, common)
- Failed water pump — Often leaks coolant from a weep hole behind the timing cover. May whine or wobble. ($400–$1,200, less common)
- Blown head gasket — White exhaust smoke, milky oil, bubbles in the coolant reservoir, or coolant loss with no visible leak. ($1,500–$3,000, less common)