Do Cars Need to Be Filled with Water?

[McNaomi]

Ordinary household cars cannot be filled with water. The engine of a car is water-cooled, but it requires specialized coolant; water cannot be used as the engine's coolant. Using water as a coolant can lead to scale buildup in the engine's water passages. Additionally, water has a relatively low boiling point and a high freezing point, making it unsuitable as a coolant. In a water-cooled engine, the coolant continuously circulates within the engine during operation to dissipate heat, thereby removing excess heat from the engine. The coolant follows two circulation paths within the engine: a major cycle and a minor cycle. When the engine starts, the coolant undergoes the minor cycle, during which it does not pass through the radiator, aiding in the engine's warm-up. After the engine has been running for a while, the coolant switches to the major cycle, passing through the radiator to dissipate heat, thus maintaining the engine within a reasonable operating temperature range. The coolant needs to be replaced periodically. If not replaced for a long time, the coolant's boiling point may decrease and its freezing point may rise, which can affect the engine's normal operation.

[Duncan]

As a seasoned driver who has owned seven or eight cars over the years, I can share some insights about "adding water" to vehicles. Cars do require "water," but not tap water or mineral water—it's specifically formulated fluids. During summer driving, dirty windshields are a common issue, so you'll need to fill the reservoir under the windshield with washer fluid. If you're too lazy to buy the dedicated solution, temporarily using tap water is acceptable, but in winter, you must switch to anti-freeze washer fluid. The small tank next to the engine is part of the cooling system, which requires coolant—this fluid prevents freezing in winter and boiling in summer, making it far more reliable than plain water. In emergencies, if coolant leaks completely, you can temporarily top it off with purified water, but you must replace it with fresh coolant as soon as possible. As for older car batteries, they used to require distilled water, but modern vehicles generally don’t need such maintenance anymore.

[McCarter]

Having worked in a repair shop for over a decade, I can tell you that adding water to a car depends on the specific part. There are two key areas under the hood: one is the windshield washer fluid reservoir, where you just add windshield washer fluid, which is cheap and available at supermarkets. The other is the pressurized coolant expansion tank with a pressure cap—this is where you add red or green antifreeze. Never use tap water here, as mineral deposits can clog the pipes and corrode metal parts. Antifreeze typically needs to be replaced every two years. Additionally, some trucks and older models may require distilled water for their batteries, but most modern passenger cars now use maintenance-free batteries, so there's no need to touch them at all. When washing your car, avoid spraying water directly into the engine compartment with high pressure—other areas can be washed without any concerns.

[OEmersyn]

When I first got my driver's license, I was also confused about whether cars needed water. I only understood after observing the mechanic's operations. The most crucial part is the engine cooling system—the small reservoir with colored liquid needs regular checks. If it's low, you should top it up with antifreeze. Windshield washer fluid is simpler: when the windshield spray stops working, pop the hood and find the small blue-capped tank to refill. The washer fluid sold in supermarkets even has bug-removing properties, which is much better than plain tap water. Nowadays, car batteries hardly need any maintenance, but remember not to spray the fuse box with a high-pressure hose when washing the car. As long as you don't pour liquid into the wrong place, water won't harm your car, but for proper maintenance, it's best to use specialized fluids.

[CorbinLynn]

Every time I perform maintenance, I check the fluids myself, and adding water requires attention to detail. The windshield washer fluid reservoir is the easiest to handle, especially in winter when choosing a -25°C antifreeze type to prevent nozzle freezing. Engine coolant must be specialized antifreeze; different colors cannot be mixed, as minerals in ordinary tap water can form scale. A special reminder for new car owners: checking the antifreeze level during the first maintenance is crucial. If you find the coolant insufficient during a long trip, you can add purified water in an emergency, but it must be completely replaced immediately upon returning home. Old-style batteries require distilled water to be added to the marked level, while newer models have built-in detection and do not require manual addition.