If your car overheats it's most likely a problem with the cooling system. Low fluid in the radiator, a broken hose, or defective thermostat can all lead to a breakdown. Other factors that can cause your car to overheat can be driving slow with the air conditioner on when it's excessively hot outside, or any number of other mechanical problems. Usually the first sign of overheating is a glowing temperature light or the gauge reading in the red zone. Another sign is steam billowing from the engine compartment. If one of these things happens, pull over and turn the heater on full blast. If this doesn't help cool the car down after a minute or so, you may as well turn the car off and wait. Avoid opening the hood or radiator cap until the temperature is down to normal. Steam from the radiator could cause serious burns. If the car cools down enough to drive again, get to the nearest service station. If you can't see any fluid in the radiator, you may want to call a tow truck.