The liquid within a vehicle's cooling system should be a 50/50 mixture of coolant and water. This mixture is designed to prevent overheating and corrosion.
When a car runs on water, a breakdown of vital mechanical parts can occur. Aside from mechanical damage, water can also reach a boiling point faster than a coolant mixture, and this causes cars to overheat easily. In the event that a car has overheated and pushed out coolant, water can be added as a temporary substitute. To add water, allow the entire car to cool, then begin adding water through the reservoir. Next, drive to the nearest repair shop so the cooling system can be repaired and the correct coolant mixture can be added.