Must the Engine Cool Down Before Adding Antifreeze?
2 Answers
Antifreeze must be added after the vehicle has been stationary and cooled down. This is because when the engine is hot, the antifreeze is under high pressure, and opening the cap may cause it to spray out, potentially causing burns. Method for replacing antifreeze: Before completely replacing the antifreeze, conduct a thorough inspection to check for any signs of leaks or cracks in the pipes, with a particular focus on the five-way hose. The five-way hose gets its name from having five connections to different parts of the vehicle. Antifreeze flows through the five-way hose and is distributed to various parts of the car to perform its function. If there is any leakage of antifreeze in this section, the hose should be replaced or the connections re-secured as needed. Drain the old antifreeze, then flush the fluid channels with clean water. Add clean water to the antifreeze reservoir and continue filling it until water flows continuously through the engine cooling system. Then, start the engine and let it idle for 3 to 5 minutes to circulate the water. Initially, the water draining from the reservoir will have a faint pink tint. Continue adding clean water until clear water flows out. Remember to disconnect the heater hose and drain the water from the heater core. Approximately one hour after draining, add the new antifreeze through the radiator hose—this allows the antifreeze 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. During this time, the coolant level will drop as air is purged from the system. Top up the antifreeze to the "MAXT" mark on the reservoir.
Yes, you must wait for the engine to cool down before adding coolant. From years of driving experience, I know the cooling system is under tremendous pressure when the engine is hot, with temperatures exceeding 100°C. Opening the radiator cap can cause steam and hot water to spray out instantly, leading to serious burns—it's no joke. I recommend waiting at least 30 minutes after turning off the engine to let the temperature drop before performing any operations to ensure safety. Checking the coolant level should also be done when the engine is cold for accurate readings. By the way, it's best to check the coolant concentration before winter arrives to prevent freezing and engine damage. Developing good habits saves time and trouble.
