Engine temperature warning lights mean stop driving immediately. The engine block, head gasket, and cooling components are designed to operate within a specific temperature range. Even 10–20°F above normal can cause permanent damage.
Common causes: coolant leak, failed water pump, failed thermostat, radiator clog, broken cooling fan, low coolant level (just from age and slow loss).
If the temperature gauge spikes or the warning light illuminates: pull off the road safely, turn off the engine, open the hood for cooling airflow. Don't open the radiator cap — pressurized hot coolant can spray with serious burn injuries.
After the engine cools (30+ minutes), check the coolant reservoir. If empty, that's likely the problem. Top up with water in a pinch (proper 50/50 coolant when possible), close hood, drive carefully to a shop watching the temperature gauge.
If overheating recurs immediately, don't continue driving. The cost of a tow ($100) is far less than the cost of a cracked head gasket ($1,500–$4,000) or full engine replacement ($5,000–$10,000+).