Should Antifreeze Be Added Directly or Should the Old One Be Drained First?
4 Answers
Whether antifreeze should be added directly or the old one should be drained first depends on the specific situation. If you are replacing it with the same brand and model of antifreeze, you can add it directly. However, if you are switching to a different brand of antifreeze, you need to thoroughly clean out the old antifreeze from the vehicle before adding the new one. Different brands of antifreeze may have varying production formulas, and mixing them could lead to chemical reactions that may affect the cooling system. The full name of antifreeze is antifreeze coolant, which means it is a coolant with antifreeze properties. It prevents the coolant from freezing during cold winter parking, which could otherwise cause the radiator to crack or damage the engine cylinder block or head due to freezing.
I have experience with coolant issues, having dealt with it recently. First, check the fluid level. If the coolant reservoir level is hovering near the minimum mark, you can simply top it up with the same brand and type of coolant, stopping at the MAX line. But remember to check the manual to confirm the coolant type first, as mixing different color formulations can cause gelling and deterioration. If your car hasn't had a coolant change in two years, or if there's flocculent sediment at the bottom of the reservoir, you must completely drain the old fluid. Last time during maintenance, the mechanic told me that expired coolant can corrode aluminum radiators, and draining the old fluid also helps flush out scale buildup in the lines. There's a drain plug at the bottom of the radiator - just unscrew it to empty the system. When adding new coolant, remember to bleed the system to prevent air bubbles.
The specific operation depends on the vehicle's condition. For new cars or those within one year, simply topping up when the fluid level is low is perfectly fine—I've done it three or four times for friends. The key is to use an antifreeze tester to check the freezing point and ensure the old and new fluids are compatible. However, extra caution is needed for older vehicles. For example, my eight-year-old SUV suddenly had a drop in fluid level last year, and upon inspection, it turned out to be a radiator leak. In such cases, adding new fluid is only a temporary fix and might even flush sediment into the cooling fins. I ended up draining all the old fluid and replacing the radiator entirely. Routine maintenance recommends a complete replacement every 40,000 kilometers or two years, as degraded antifreeze can raise the freezing point, risking pipe cracks in severe winters.
This is a common issue, let me summarize the key points: For short-term minor loss, simply top it up, but be sure to use the OEM coolant of the same color. If the coolant appears black, cloudy, or has sediment, it indicates the corrosion inhibitors have failed, requiring a complete drain and replacement. Remember to operate when the engine is cold, loosen the drain plug underneath the vehicle, and empty the plastic reservoir as well. Refer to the manual for the amount of new coolant to add; generally, sedans require about 6 liters. Finally, start the car and let the engine run to bleed air from the cooling system. Doing it yourself can save you around 300 yuan in labor costs; just buy a reputable brand of coolant.
