What happens if you add a bottle of mineral water when the coolant is insufficient?
2 Answers
Adding a bottle of mineral water when the coolant is insufficient can cause the freezing point of the antifreeze to rise. The mineral water may react chemically with the components in the antifreeze, affecting its functions such as anti-boiling, anti-corrosion, anti-scaling, and lubricating the cooling system. The main components of coolant are ethylene glycol and water, and the water must be pure water, not mineral water or tap water. If the coolant is insufficient, you can add pure water or distilled water. If the antifreeze is fully replenished, it will gradually be lost during use. If the loss is not caused by leakage, you can add pure water or distilled water to the antifreeze. This is because, when using the car, ethylene glycol does not evaporate—only water does—so adding water to the antifreeze is not a problem.
Last time I went on a long trip, I ran low on coolant and hastily added a bottle of mineral water to make it home. It worked fine at first, but within days, big trouble emerged. The impurities in the mineral water, like calcium and magnesium, precipitated into scale, clogging the small channels in the radiator and engine. With the water flow obstructed, the temperature skyrocketed, and the engine overheating warning light kept flashing. The worst part was the corrosion—aluminum components are prone to damage from substances in the water. Later, my car's radiator started leaking, and when it was repaired, a bunch of rust debris was found inside, costing me over 2,000 yuan to fix. It’s not that you can’t use it as a short-term emergency measure, but the risks are too high. Now, I always keep a small bottle of distilled water or premixed coolant in my car. Lesson learned—checking the coolant level before driving has become my habit. Safety first—don’t skimp on this small expense.
