Overheating
Temperature climbing, coolant boiling, heater blowing cold. Diagnose quickly to prevent head gasket damage.
HIGH RISK
Common symptoms
- Temp gauge rising
- Coolant smell/steam
- Heater goes cold
- Fans running constantly
Cost expectations
DIY: £0–£120 (tests/thermostat). Garage: £150–£900+ if major damage.
Note: prices vary by car and region. Use this as a planning range.
Most likely causes (ranked)
- Coolant leak — Hose, radiator, water pump, housing.
- Thermostat stuck — Blocks flow or opens late.
- Airlock — After coolant work or slow leak.
- Radiator/fan fault — No airflow at low speed.
- Head gasket issue — If repeated overheating or pressurising coolant.
Quick checks (fast, low-cost)
- Do not keep driving if temp climbs rapidly.
- Check coolant level when cold; look for external leaks.
- Pressure test cooling system to find leaks.
- Use IR thermometer to compare radiator inlet/outlet temps.
- Check fans engage at expected temps.
Recommended tools
These tools make diagnosis faster and stop you buying random parts.
Related fixes
If your symptoms don’t match perfectly, check these next.
What to do next
- Stop driving if overheating continues.
- Fix leaks/airlocks first.
- If coolant pressurises quickly, investigate head gasket.
AutoSolveHub helps you narrow possibilities. Always confirm critical repairs with proper testing and safe procedures.