What Causes Antifreeze to Fade in Color?
2 Answers
The reasons for antifreeze fading in color include prolonged use leading to oxidation reactions, contamination by other liquids, or deterioration and impurity accumulation in the antifreeze. When antifreeze color fading is observed, it is recommended to replace the antifreeze. A lightened color indicates that the antifreeze has begun to deteriorate. The main components of antifreeze are 50% pure water, 40% methanol, and 10% other substances. Antifreeze is generally categorized into three types: ethanol-water, glycerol-water, and ethylene glycol-water. Method for replacing antifreeze: Before completely replacing the antifreeze, conduct a thorough inspection to check for any signs of leakage or cracks in the pipes, with particular attention to the five-way hose. The five-way hose is named for its five connections to various parts, and antifreeze is distributed to different parts of the car through this hose to perform its function. If there is any leakage of antifreeze in this section, replace the hose or resecure the connections as needed. Drain the old antifreeze, then flush the liquid channels with clean water. Add clean water to the antifreeze reservoir, then continuously flush the engine cooling system with water. Start the engine and let it idle for 3 to 5 minutes to circulate the water. Initially, the water draining from the reservoir may have a faint pink color. Continue adding clean water until the outflowing water is clear. Remember to remove the heater hose and drain the water from the heater core. After draining for about an hour, add the new antifreeze through the radiator hose to allow it to flow quickly into the radiator. Then, add another container of antifreeze to the antifreeze reservoir until it is nearly full. Start the engine and let it run for about 10 minutes. As some air is expelled from the cooling system, the fluid level will drop. Add more antifreeze until it reaches the "MAXT" mark on the reservoir.
Last time I checked my car, I noticed the coolant had faded from bright green to a lighter shade. My mechanic friend explained that this happens because the additives degrade over time, causing the color to disappear. If the coolant is exposed to high temperatures for too long, such as during long summer drives, thermal decomposition can cause the dye to lose its effectiveness. Contamination, like mixing with engine oil or impurities in the cooling system, can also lead to discoloration—I once experienced oil leakage turning the coolant gray and cloudy. Such changes often signal internal system issues, such as rust or sediment buildup. Ignoring them could clog the coolant passages and cause overheating. I recommend replacing the coolant every two years with a high-quality brand, diluted with distilled water for stability. If you notice any discoloration, address it promptly to avoid engine damage.
