The engine is the “heart” of a truck, and coolant is the “lifeline” that cools it. Many truck drivers believe that “tap water can also dissipate heat, so I’ll use it instead of coolant to save money.”
However, the reality is that many vehicle overheating, cylinder block cracking, and pipe blockages stem from this seemingly “cost-saving” practice.
So, what exactly is the difference between tap water and coolant?
1. The Hidden Dangers of Using Tap Water as Coolant
The core function of coolant is to continuously remove the high-temperature heat generated by the engine during operation, ensuring the engine operates within its normal temperature range.
While tap water can indeed provide some cooling, it lacks many crucial skills compared to professional coolant—not only can it not handle extreme temperatures, but it can also quietly damage the cooling system. Over time, small problems can escalate into major malfunctions, resulting in higher repair costs.
2. Two Major Drawbacks of Tap Water
(1) Insufficient Boiling Point: In summer or during high-intensity operations, tap water boils over quickly. We all know that the boiling point of tap water under standard atmospheric pressure is 100℃. However, when a truck engine is running, especially during long-distance travel or heavy loads in summer, the temperature inside the cooling system can easily exceed 100℃.
If tap water is used at this time, it will boil rapidly upon reaching its boiling point, commonly known as “boiling over.” This not only interrupts engine cooling but can also cause piston and cylinder deformation in severe cases.
Professional coolants, on the other hand, typically have a boiling point of around 110℃, easily withstanding high-temperature environments and keeping the engine at a safe operating temperature.
(2) Inadequate Freezing Point: In winter or in cold regions, tap water freezes and cracks easily. Coolant also has an important function—antifreeze.
For the cooling system to circulate properly, the liquid must remain fluid. Once it freezes, its expansion can directly crack the radiator and engine block, resulting in repairs costing anywhere from several thousand to tens of thousands of yuan.
Qualified coolant typically has a freezing point between -15℃ and -45℃. Truck drivers should choose the appropriate model based on their local lowest temperature to avoid freezing even in the coldest winter.
However, adding tap water to the cooling system, even in small amounts, will significantly lower the overall freezing point. At sub-zero temperatures, the risk of freezing doubles.
3. Coolant can “protect the vehicle”
Besides temperature control, coolant contains specialized chemical components. These “small ingredients” are key to protecting the cooling system, while tap water completely lacks these functions:
(1) Corrosion prevention: Protecting metal parts from rusting. Engine and cooling system components, such as the engine block, radiator, and pipes, are mostly made of metals such as copper, iron, aluminum, and steel.
When these metals come into contact with tap water at high temperatures, they will oxidize over time, leading to rust and corrosion. This can range from affecting heat dissipation to causing component damage and leaks.
The corrosion inhibitors in coolant form a protective film on the metal surface, preventing oxidation and even slightly removing rust, essentially providing “maintenance” for the cooling system.
(2) Preventing scale buildup: Avoiding pipe blockage and saving cleaning hassle. Tap water contains trace elements and impurities such as calcium and magnesium. Under high temperatures, these substances slowly deposit on the inner wall of the water tank and the surface of the cylinder liner, forming a thick layer of scale.
Scale not only acts as an “insulation layer” affecting heat dissipation but also clogs small circulation pipes, causing poor cooling system circulation.
More troublesome is that scale has strong adhesion, requiring specialized tools and chemicals for cleaning, which is both time-consuming and expensive.
Coolant itself does not easily produce scale, allowing the cooling system to remain unobstructed for a long time.
4. Change Coolant Regularly
A point easily overlooked: coolant isn’t a one-time fill and can be used for a lifetime; it has a defined lifespan (usually 2-3 years or 40,000-60,000 kilometers, depending on the product instructions).
After its expiration date, the additives in the coolant will become ineffective, and its temperature control and corrosion prevention functions will significantly decrease, making it essentially no different from ordinary tap water. Continuing to use it carries the same risks.
Therefore, truck drivers must regularly check the coolant’s condition and replace it on time when it expires. Also, don’t be tempted to buy cheap, low-quality coolant; these products may have substandard additives, which not only fail to provide protection but may also accelerate component corrosion, ultimately resulting in more harm than good.
