You are driving along and you notice that your engine temperature gauge is going into the red indicating engine overheating.  You pull over and smoke starts pouring out of the hood.  Why is the car overheating and what should you do next? 

The vehicle is most likely overheating because there is a coolant leak that has reduced the fluid in the cooling system.  Without fluid to cool the engine overheating is usually inevitable.  So the first thing you need to do is shut off the car and let it cool down. This will probably take around half hour, so be patient.  Operating a car when the engine is overheating can cause severe and costly damage to the engine.  The coolant will probably be low.  Since you most likely do not have any coolant with you, and because most manufacturers now have their own specific types of coolant which should not be mixed with other types of coolant, the safest course of action is to add water into the coolant overflow bottle until it measures full. Then start the engine and proceed immediately to an automotive repair shop.  The repair shop will determine where the fluid loss is coming from and what repairs are necessary.  Repairs can be as simple as replacing a faulty clamp or hose, or more complicated (and costly) such as replacing the radiator itself.  Most radiators in today’s vehicles are metal/plastic combinations that can not be repaired as was the case years ago.

If the vehicle is overheating and the coolant level is full the most likely explanation is the thermostat is stuck closed and the coolant is not circulating through the engine.   In this case the thermostat will need to be replaced.

If you can not drive your car to a repair shop before it overheats again, then call a tow company so you do not cause costly damage to you engine. Never, ever, add coolants of different colors together as the resulting mixture may cause damage to your cooling system.