Pull safely off the road, preferably into a rest area or on the road shoulder. Turn on you hazard lights, put your car in neutral (manual) or park (automatic) and apply the parking brake. Turn off the air conditioning if it is being used. Leave the engine running.
2Check for steam or engine coolant boiling over from under the hood/bonnet, and from the radiator and reservoir. If there is steam or engine coolant boiling over, stop the engine and wait until it subsides before proceeding.
3Carefully open the hood/bonnet of your vehicle. Check again if there is any coolant or steam coming out of your radiator or reservoir. Stop the engine if there is, and wait until it subsides.
4Check if the engine cooling fan is operating. It is located directly behind the radiator, and is used to bring air through the radiator to cool the water when there is insufficient natural air flow. If the fan is not operating, stop the engine.
5Inspect your engine drive belts at the front of the engine to see if any are broken or loose. The main belt (usually closest to the engine) drives the water pump and the alternator/generator. If the belt is loose or broken, the water pump will not operate and cooling water is not being pumped through the system. If this is the case, stop the engine immediately and call a mechanic.
6Look for obvious leaks from your radiator, and the radiator hoses connecting the radiator to the engine. Also check under your vehicle for obvious leaks. Note that if you were using the air conditioning, it is normal for water to be draining from the air conditioning unit. If coolant is leaking, stop the engine and call a mechanic.