What Causes the Continuous Decrease in Antifreeze?
3 Answers
Antifreeze gradually decreases for the following reasons: I. Function of Antifreeze: Cooling is the basic function of coolant. When the engine is running, it generates a large amount of heat, with 60% of this heat being dissipated into the surrounding space through the cooling system. Water and methanol coolants have low boiling points and are prone to boiling. If the vehicle operates under conditions where the coolant boils, even for a short period, it can cause engine damage or even failure. In winter, when temperatures are low, substances that lower the freezing point of water are added as antifreeze to ensure the cooling system does not freeze in cold weather. Hence, coolant is sometimes referred to as "antifreeze" or "non-freezing liquid." II. Reasons for Rapid Consumption: 1. Leakage, where the leakage points usually have very obvious traces. 2. Poor circulation leading to rapid consumption; it is advisable to have a professional mechanic inspect the system. When adding antifreeze, ensure the engine has cooled down. During the addition process, start the engine and gently press the accelerator to expel air from the system. Add the coolant slowly to ensure it is fully filled. If necessary, follow the manual's instructions to bleed the cooling system. 3. Antifreeze entering the cylinder and mixing with the oil. In mild cases, there may be no water in the oil pan, but performance may be affected. In severe cases, water in the oil pan can cause unstable engine operation. Do not immediately assume the issue is with the cylinder head gasket; a damaged intake manifold gasket can also cause coolant to enter the cylinder, as some engines have water channels in the intake manifold. III. Symptoms of Decreasing Antifreeze: 1. A gradual decrease in coolant level in the external reservoir of the engine cooling system is normal. Generally, coolant should be replaced every 40,000 kilometers. As long as the coolant level in the reservoir remains above the minimum mark during the maintenance cycle, no additional coolant is needed. Proper maintenance involves checking the coolant level in the external reservoir every 5,000 kilometers. 2. Modern car engine cooling systems typically do not exhibit significant internal leaks. Leaks usually occur between the cylinder head and cylinder block, water pump housing and cylinder block, water pump shaft seal, and the junction between the thermostat valve cover and the manifold. Leaks between the cylinder head and cylinder block can cause internal seepage, while other leaks are external. Significant leaks, whether internal or external, are easily detectable. External leaks leave traces, while internal leaks may cause white smoke from the exhaust pipe or water accumulation in the oil pan. 3. Micro-leaks are high-temperature, high-pressure vapor micro-leaks, mainly occurring at the connections between the radiator's inlet and outlet hoses and metal pipes (radiator, engine inlet and outlet), radiator cap, and reservoir cap.
I just dealt with this issue last week. If the coolant is secretly decreasing, it's most likely leaking from somewhere. Focus on three key areas: the water pump under the engine is the most prone to leaks, especially for cars over five years old—the shaft seal can age and drip water. Next, check the seams and corners of the radiator, particularly spots hit by road debris like pebbles. The most troublesome issue is if the head gasket is damaged—coolant can seep into the engine and burn off, causing white smoke from the exhaust with a slightly sweet smell. In this case, a major repair is needed. Don’t just keep topping up the fluid; finding and fixing the leak early saves headaches. If too much leaks, the engine can overheat and fail.
After ten years of car repair, I've encountered too many cases of coolant disappearance. First, crawl under the car to check for pink or green water stains on the ground—if there's a leak, it's easy to spot. If no obvious leak is found, inspect the heater hoses, which are hard to notice near the firewall. Then squeeze the upper and lower radiator hoses; if they feel sticky or swollen, they need replacement. Another hidden issue is tiny cracks in the auxiliary coolant reservoir, which only leak steam at high temperatures. Here's a trick: stuff a tissue into the reservoir cap when the engine is cold. If the tissue gets wet after driving ten kilometers, it's a steam leak.
