What are the consequences of adding tap water to the engine radiator?

[CollinRose]

Adding tap water to the engine radiator can cause the car to malfunction due to excessive temperature. The following are the specific reasons and methods for dealing with radiator boiling: Reasons: The car radiator is the main component of the car's cooling system. The car radiator should not come into contact with any acid, alkali, or other corrosive substances to prevent aging. Soft water should be used in the radiator. Hard water needs to be softened before use to avoid internal blockage and scale formation in the car radiator. It is recommended to choose long-lasting antifreeze that meets national standards and is produced by reputable manufacturers. Tap water tends to produce more rust, which is detrimental to the smoothness of the engine's water passages. Handling radiator boiling: If the temperature gauge rises during driving, choose a safe place to stop immediately, turn off the engine, and open the hood to help the engine cool down. After about half an hour, the engine temperature will return to normal. Then, carefully check the radiator scale and whether the fan is damaged. If the radiator is low on water, you can add purified water or antifreeze after it has cooled for a while. Do not add cold water directly. Always use a wet towel to cushion the opening of the radiator cap to prevent steam burns.

[MacEverly]

I've been driving for twenty years, and what I fear most is radiator problems. Once, a friend's car overheated on the road, and he couldn't find coolant, so he used tap water as a temporary fix. A month later, the engine needed a major overhaul, and when it was opened up, it was full of yellowish-brown scale. Tap water contains many impurities, and when boiled, it forms scale deposits that gradually clog the radiator's water channels, which are finer than a strand of hair. At high temperatures, it's also prone to vaporization and boiling, reducing cooling efficiency by 30%. The worst part is the corrosion of metal components; aluminum alloy radiator joints can oxidize and develop holes. In winter, when temperatures drop below freezing, it's even worse—ice can expand and crack the engine block. After that incident, he started replacing the entire coolant system every six months and never dared to cut corners again.

[StElliot]

During car repairs, we often encounter vehicles with failures caused by adding water. When the engine is running, the metal surface temperature exceeds 90°C, and tap water evaporates at high temperatures, leaving behind scale deposits. These white crystals are like blood clots in blood vessels. After the cooling passages become blocked, heat dissipation deteriorates, and the piston rings may deform due to high temperatures, leading to cylinder scoring. In the most severe case we've disassembled, the water pump impeller was completely jammed by rust and scale. The slightly acidic pH of tap water can corrode the radiator solder joints, and leakage is only a matter of time. Adding water in an emergency can last at most 200 kilometers. Once at the repair shop, the entire system must be drained, flushed with professional cleaning agents, and then refilled with coolant. It is recommended to always keep a bottle of concentrated coolant in the trunk.

[LaIvan]

Last time I borrowed a friend's car for a long-distance trip and noticed the coolant level was low, so I casually added a bottle of mineral water. On the way back, the temperature gauge shot up to the red line, forcing me to make an emergency stop for inspection. The mechanic pointed at the fogged-up overflow tank and explained that the calcium deposits from such hard water would crystallize on the thermostat. Even worse, the electrolytic properties of tap water create galvanic reactions between different metal components. Using an endoscope, he showed me how the radiator fins had turned brown in just two months. Now I make it a habit to check the antifreeze's freezing point monthly and replace fully synthetic coolant regularly. Remember, topping up with water might seem harmless for short trips, but drive two continuous hours on the highway and problems will surely surface.