Understanding the functions and precautions of antifreeze

Antifreeze Guide

The full name of antifreeze is antifreeze coolant, which means coolant with antifreeze function. It prevents coolant from freezing and cracking the radiator, and it also helps prevent freezing damage to the engine cylinder block or cap during cold winter parking.

Many people think antifreeze is only used in winter, but antifreeze should be used all year round. It supports freezing protection, boiling protection, corrosion prevention, scale control, and normal engine temperature management.

Basics

Chemical composition and types

Most water-based antifreeze uses ethylene glycol

More than 95% of water-based antifreeze at home and abroad uses ethylene glycol. Compared with tap water, the most significant feature of ethylene glycol is antifreeze ability, while water cannot prevent freezing.

Ethylene glycol also has a high boiling point, low volatility, moderate viscosity, little change with temperature, and good thermal stability. For these reasons, glycol-type antifreeze is an ideal coolant.

There are many kinds of antifreeze materials. Examples include calcium chloride (CaCl2) in inorganic substances, methanol (CH3OH), ethanol (C2H5OH, commonly known as alcohol), ethylene glycol (C2H4(OH)2, commonly known as sweet alcohol), propanetriol (C3H5(OH)3, commonly known as glycerin), lubricating oil, sugar, and honey.

These substances are common in daily life and can be used as the mother liquor of antifreeze. After adding an appropriate amount of pure soft water, such as distilled water, unpolluted rainwater, or snow water, antifreeze in the general sense can be formed. The water should have no or only a small amount of calcium and magnesium ions, with total hardness component concentration between 0-30ppm.

Because methanol and ethanol are more volatile, they are not suitable for use in northern vehicles.

Core Functions

Functions of antifreeze

Antifreeze protects the cooling system in more ways than freezing prevention

In addition to antifreeze protection, antifreeze has several important advantages. It provides anti-corrosion protection for the engine and cooling system, helps prevent rust, supports anti-boiling performance, and helps control limescale.

The engine and cooling system are made of metals including copper, iron, aluminum, steel, and solder. When these metals contact water at high temperatures, they corrode and rust over time. Antifreeze does not cause corrosion to the engine cooling system and also supports corrosion prevention and rust removal.

Antifreeze can be used in automobiles, train internal combustion locomotives, tractors, ships, engines, water tanks, mechanical equipment, diesel engines, gasoline engines, and other cooling systems. It provides functions such as anti-freezing, anti-boiling, anti-corrosion, and water-scale control.

The boiling point of water is 100℃, while the boiling point of high-quality antifreeze coolant is usually above 110℃. This means that in summer, antifreeze coolant is more difficult to boil than water.

Drivers using water as coolant often face the problem of limescale. Scale adheres to the metal surface of the water tank and water jacket, making the cooling effect worse and becoming difficult to remove. High-quality antifreeze is made with distilled water and anti-scaling additives, so it does not produce scale and can also have a descaling function.

If the water tank scale is very thick, it is best to use a tank cleaner to clean thoroughly before adding antifreeze. Like water, antifreeze has the advantages of large specific heat, high latent heat of evaporation, and easy replenishment.

When the ambient temperature is below zero, water in the cooling system can turn into ice. The cooling system components then face the risk of expansion and cracking. Antifreeze helps ensure that the engine works normally at low temperatures.

Modern automobile engines operate at higher temperatures than older engines. The normal upper limit of the working temperature is generally more than 100℃. For example, the normal working temperature of a Shanghai Santana engine is 90℃-105℃, FAW Jetta is 85℃-115℃, and Fu Kang is 90℃-118℃.

If only water is added, the water will boil when engine temperature reaches 100℃. Water is also corrosive and produces scale that affects the cooling effect. Therefore, a special cooling medium, antifreeze, is needed.

Some people think antifreeze is only for vehicles in cold areas, but this is a misunderstanding. The main component of most antifreeze on the market is ethylene glycol, which has a high boiling point and a low freezing point. Antifreeze also contains additives to prevent glycol oxidation, prevent corrosion, and prevent foam.

Protective effect

Anti-corrosion protectionIt protects components of the cooling system from corrosion.
Scale preventionIt helps prevent limescale and avoids reducing radiator cooling effect.
Normal temperature rangeIt helps ensure that the engine works within the normal temperature range.

Engine antifreeze must have the characteristics of antifreeze protection, anti-boiling performance, anti-corrosion protection, water-scale prevention, no foam, and stable use across seasons and regions. Among these characteristics, freezing point and boiling point are the basic indicators of antifreeze.

Selection

Selection and correct use

Choose antifreeze by quality, freezing point, boiling point and manufacturer requirements

The quality of antifreeze matters. If antifreeze is poor-quality or counterfeit, it cannot play the proper role. Coolant is prepared by mixing antifreeze with water in a certain ratio. Auto manufacturers usually specify antifreeze mixture ratios for different low-temperature grades in the user manual, and they also specify the antifreeze type, which should not be mixed.

In general, when the ratio of antifreeze to water is 40:60, the boiling point of the coolant is 106℃ and the freezing point is -26℃. When the ratio is 50:50, the boiling point of the coolant is 108℃ and the freezing point is -38℃.

The general requirement is to prepare coolant according to the minimum local temperature with about five ℃ margin. Antifreeze has an effective use period of more than two years. If it expires or the coolant is found dirty, it should be replaced. When replacing old coolant, add clean water, start the engine, idle for about ten minutes for circulation cleaning, stop the engine, and then drain the clean water.

When filling new coolant, do it while the machine is cold. Fill the coolant to the highest mark of the reservoir, marked “MAXT,” then screw the cover on, start the engine, idle until normal engine temperature, and turn off the engine. When the body temperature drops, check the reservoir fluid level and maintain it at the “MAXT” position. If it is not enough, replenish until enough.

According to the survey in the original article, more than 50% of global car engine failure comes from the cooling system. This shows the importance of reasonable antifreeze matching. Most antifreeze sold in the market uses ethylene glycol as the main raw material, then adds the right amount of organic or inorganic salts to provide corrosion and rust prevention.

As weather turns colder, the water tank is prone to freezing and cracking, so choosing antifreeze is important for the health of the car’s engine. Automotive antifreeze coolant has anti-freezing function in winter and anti-boiling function in summer. It protects the engine cooling system, improves heat dissipation, and increases engine efficiency.

The lower the freezing point, the stronger the antifreeze performance. Usually, the selected freezing point should be more than 10℃ below the minimum local temperature to prepare for sudden weather changes. For example, Great Wall Lubricant multi-effect antifreeze has a freezing point range from -25℃ to -50℃, which can meet the demand for vehicle antifreeze in most northern regions of China.

When choosing specifications such as -15℃, -25℃, -30℃, or -40℃ antifreeze, it is generally appropriate to choose one more than 10℃ lower than the lowest temperature in the region. In Beijing, -30℃ antifreeze is generally chosen.

Also pay attention to the anti-corrosion function. Many antifreeze products are sold on the market, and quality can be mixed. Some small factories may only measure the freezing point before putting antifreeze on the market.

Antifreeze is not the purer, the better. Do not directly inject antifreeze mother liquor. Direct injection may cause antifreeze deterioration, increased low-temperature viscosity, and abnormal engine temperature, affecting vehicle service life.

The engine cooling system must be cleaned before refilling antifreeze. Antifreeze can descale. If it is added directly to a dirty system, shedding scale may block water pipes and cause poor heat dissipation.

Finally, tap water should not be used to dilute antifreeze. Scale and impurities in tap water may react with antifreeze additives and create precipitation.

Replacement

Replacement, inspection and filling

Inspect, drain, flush and refill antifreeze carefully

Replacement interval

For vehicles that run for a long time, such as cabs, high-quality antifreeze is generally replaced once a year. Vehicles with shorter running time can generally replace it every two years or every 30,000 km.

To prevent excessive foam generation and reduce poor heat exchange between coolant and engine parts, confirm that the product is within its validity period when adding antifreeze. Long-lasting antifreeze can have a validity period of up to three years. If suspended matter, sediment, deterioration, or discoloration is found, replace the antifreeze and clean the system in time.

Inspection before replacement

Before completely replacing antifreeze, perform a thorough inspection. Check each pipe for signs of leakage and cracks, focusing on the five-way pipe. It is called a five-way pipe because it has five interfaces connecting various parts of the tube.

Antifreeze is distributed to different parts of the car after flowing through the five-way pipe. If antifreeze leakage is found in this part, replace the water pipe or re-fix the interface according to the situation.

Drain the old antifreeze and clean the passages

Drain the old antifreeze and clean the fluid passages with clean water. Add fresh water to the antifreeze refill tank and continue filling with freshwater so that it flows through the engine cooling system. Then idle the car for 3 to 5 minutes to let the water circulate.

At first, the water from the tank may be light pink. Continue adding water until the water flowing out is clean. Do not forget to remove the heater hose to drain water from the heater tank.

Add new antifreeze

After draining the water for about 1 hour, add new antifreeze from the water tank or radiator hose. This helps the antifreeze enter the tank quickly.

Then add another bucket of antifreeze into the antifreeze tank until the tank is almost full. Run the car for about 10 minutes. At this time, the cooling system level may drop because some air has been eliminated. Add antifreeze again and fill the tank to the highest mark, “MAXT.”

Practical Checklist

Key antifreeze precautions from the article

Choosing antifreeze

Use all yearAntifreeze is not only for winter; it also helps prevent boiling, corrosion, scale, and foam.
Follow the manualUse the antifreeze type and mixture ratio specified by the vehicle manufacturer.
Check freezing pointChoose a freezing point more than 10℃ below the lowest local temperature.
Avoid mixingDo not mix incompatible antifreeze types or use counterfeit products.

Replacing antifreeze

Inspect firstCheck pipes, cracks, leakage, and the five-way pipe before replacing.
Flush cleanDrain old antifreeze and circulate clean water until the outflow is clean.
Fill coldAdd new coolant while the machine is cold and watch the reservoir mark.
Recheck MAXTAfter air is eliminated and the level drops, refill to the highest “MAXT” mark.

Summary

Antifreeze protects the cooling system in every season

Antifreeze coolant protects the engine cooling system from freezing, boiling, corrosion, rust, scale, and foam. Because modern engines often work near or above 100℃, coolant selection affects both winter starting safety and summer heat control.

Choose antifreeze according to quality, freezing point, boiling point, manufacturer specification, mixture ratio, and local minimum temperature. When replacing it, inspect for leaks, flush the system, avoid tap-water dilution, and refill to the proper “MAXT” level after the air is eliminated.