Can water be added to car coolant?
2 Answers
Water should not be added to car coolant. Adding water to coolant will lower the boiling point of the new coolant, which may cause the car to overheat. The main component of coolant is ethylene glycol, which has good thermal stability, preventing freezing in winter to protect the engine from damage, and cooling the engine in summer to ensure it operates at suitable temperatures year-round. These effects cannot be achieved by simply adding water. Coolant has functions such as antifreeze, cooling, anticorrosion, and anti-scaling. Although coolant also contains water, this water is soft water, also known as distilled water, which has undergone deionization and softening treatment. If the car engine coolant is insufficient, soft water can be added, but the amount should be carefully controlled to avoid adding too much, as this can alter the boiling and freezing points of the coolant.
I've encountered this situation before. The mechanic told me that you should never casually add tap water to coolant. In an emergency, only distilled water can be used as a temporary solution. The calcium and magnesium ions in tap water can form scale deposits under the high temperatures of the engine. These deposits can clog the engine's water passages and radiator fins, essentially putting a 'warm mask' on the engine. Over time, this can reduce cooling efficiency by up to 30% and also corrode the water pump's seals. When driving in northern regions, I pay special attention to the freezing point. Diluting with water lowers the antifreeze capability, and frozen pipes in winter can cost thousands in repairs. Now, I always keep two bottles of original coolant in the trunk and follow the maintenance manual for regular replacements—it's the most hassle-free way.
