What is antifreeze coolant?
1The full name of coolant should be antifreeze coolant, meaning it has antifreeze properties. Coolant prevents freezing and cracking of the radiator and engine cylinder block during cold weather when the vehicle is parked. However, it's important to correct a misconception: coolant is not just for winter use; it should be used year-round. In regular vehicle maintenance, the engine coolant should be replaced approximately every year of driving.
1. Characteristics of Antifreeze Coolant
1Antifreeze has multiple functions such as preventing freezing, boiling, corrosion, and scale formation. Like water, it offers advantages such as high specific heat capacity, high latent heat of evaporation, and easy replenishment. When the ambient temperature drops below 0°C, the water in the cooling system can turn into ice, posing a risk of expansion and damage to the system. Using antifreeze ensures the engine operates normally even in low temperatures.
2. Function of Antifreeze Coolant
1. Winter freeze prevention
1To prevent the coolant from freezing after a car is parked in winter, which could cause the radiator and engine block to crack due to expansion, the freezing point of the coolant should be approximately 10°C lower than the lowest temperature in the region, in preparation for sudden weather changes.
2. Corrosion prevention
1In the cooling system, components such as the radiator, water pump, cylinder block and head, and water distribution pipe are made of metals including steel, cast iron, brass, copper, aluminum, and solder. Due to the different electrodes and potentials of these metals, electrochemical corrosion is prone to occur under the action of electrolytes. Additionally, acidic byproducts formed from the decomposition of glycol-based substances in the coolant, as well as acidic exhaust gases produced by fuel combustion, may infiltrate the cooling system, leading to corrosion.
1Corrosion in the cooling system can cause failures in the lower water chamber of the radiator, fuel injector sleeves, cooling pipes, joints, and radiator tubes. Additionally, corrosion products can clog the pipes, leading to engine overheating or even breakdown. If corrosion causes perforation, coolant leaking into the combustion chamber or crankcase can result in severe damage, as mixing coolant or water with lubricating oil produces sludge and gum, weakening lubrication and causing valves, hydraulic valve lifters, and piston rings to stick. Therefore, a certain amount of anti-corrosion additive is added to the coolant to prevent corrosion in the cooling system.
3. Anti-scale
1The coolant should minimize scale formation during circulation to prevent clogging of the circulation pipes and impair the cooling system's heat dissipation function.
4. High boiling point (anti-boil over)
1Coolant that meets the standard typically has a boiling point exceeding 105°C, which is higher than water's boiling point of 100°C. This allows the coolant to withstand higher temperatures without boiling (overheating), to some extent meeting the cooling needs of high-load engines.
3. Classification of Coolants
1Coolant consists of three parts: water, antifreeze, and additives. Depending on the type of antifreeze, it can be classified into alcohol-based, glycerol-based, ethylene glycol-based, and other types of coolant.
(1) Alcohol-based coolant
1It uses ethanol (commonly known as alcohol) as an antifreeze, which is inexpensive, has good fluidity, and simple preparation process. However, due to its low boiling point, easy evaporation loss, tendency for the freezing point to rise, and flammability, it has gradually been phased out.
(2) Glycerol-based coolant
1High boiling point, low volatility, non-flammable, non-toxic, and minimal corrosiveness, but poor effectiveness in lowering freezing points, high cost, and expensive, making it difficult for users to accept, with only a few Nordic countries still in use.
(3) Ethylene glycol-based coolant
1It uses ethylene glycol as an antifreeze agent, with a small amount of comprehensive additives such as anti-foaming and anti-corrosion agents added. Ethylene glycol is highly soluble in water, allowing it to be formulated into coolants with various freezing points, with the lowest freezing point reaching -68°C. This type of coolant features a high boiling point, low foaming tendency, excellent viscosity-temperature performance, and anti-corrosion and anti-scaling properties, making it an ideal coolant. Currently, almost all coolants used in engines domestically and internationally, as well as those sold in the market, are this ethylene glycol-based coolant.
IV. Engine Coolant Color
1Red/Orange - contains propylene glycol; Green - contains ethylene glycol; Gold - long-life antifreeze coolant. A good coolant has a bright color, close to the standard hue, and emits a pleasant aroma. If the coolant appears grayish-white or brown, it indicates that the coolant has deteriorated.
5. Usage status of engine coolant
(1) Use coolant consistently throughout the year.
1For traditional engines, the coolant temperature that ensures normal operation is maintained between 80°C and 90°C. However, for electronically controlled engines, due to their high-speed, high-compression ratio, and high-power operating characteristics, they experience greater mechanical and thermal loads, along with higher frictional heat. Consequently, the required normal operating temperature for the coolant has been raised to 95°C to 105°C. This differs from the conventional understanding of "normal coolant temperature" for traditional engines, necessitating a shift in perception.
1Moreover, it is important to maintain the continuous use of coolant. The notion of only using coolant in winter is incorrect, as it overlooks the coolant's functions of anti-corrosion, anti-boiling, and anti-scaling, focusing solely on its anti-freezing properties.
(2) Proper selection of coolant
1When selecting the appropriate coolant, its freezing point should be about 10°C lower than the minimum ambient temperature. The automotive parts market offers a variety of coolants, but what is labeled as "coolant" is often just "antifreeze," mostly made by mixing alcohols with water and adding dyes. These products lack any additives that a proper coolant should contain, have a boiling point around 90°C, are highly corrosive, and can easily lead to engine overheating.
1High-quality coolant is brightly colored, clear, transparent, and odorless; when heated in a beaker and its boiling point measured with a thermometer, only those with a boiling point above 100°C are genuine.
Selection and Usage Recommendations
In summary, caution should be exercised when selecting and adding coolant. First, choose the appropriate coolant ratio based on specific conditions. Second, add the selected coolant to the reservoir until the liquid level reaches the specified position.
Antifreeze coolant is an indispensable and crucial component for the normal operation of an engine. Proper selection and use of antifreeze coolant not only ensure the engine functions correctly under various working conditions but also effectively extend the service life of the engine and its cooling system.
