Will the antifreeze evaporate if the cap is not tightened properly?
2 Answers
It will increase the evaporation of the antifreeze level. Since the antifreeze continuously heats up during driving, the liquid level of the antifreeze will drop more quickly; it may also cause the antifreeze to overflow while driving. The primary function of the radiator cap is to provide a seal. If the seal is not tight, driving on bumpy roads can easily cause the antifreeze to overflow from the reservoir. Replacement cycle of antifreeze: Vehicle antifreeze generally needs to be replaced every 2 years or 40,000 kilometers. This is just a reference cycle. For commercial vehicles with longer mileage, the replacement cycle is shorter. Since the driving conditions of each vehicle vary, the replacement should be based on actual usage. Check the condition of the antifreeze. If the antifreeze is insufficient, replenish it promptly. If suspended matter, sediment, or deterioration/discoloration is found in the antifreeze, replace it immediately and clean the system. How to choose antifreeze: The basic indicators of antifreeze are the freezing point and boiling point. On the market, antifreeze is available in freezing points such as -15°C, -25°C, -30°C, -40°C, etc. Generally, it is advisable to choose one that is at least 10°C lower than the lowest temperature in your region.
A few days ago, my neighbor's kid forgot to tighten the antifreeze cap, and white smoke started coming out of the engine bay, which really scared me. The biggest issue with a loose cap isn't evaporation, but rather the leakage of cooling system pressure. When the engine is running, the antifreeze temperature can exceed 90°C. Under normal pressure, the boiling point rises to around 120°C, but if the cap is loose, it drops back to about 100°C, causing the antifreeze to boil and turn into steam, which then sprays out. Last month, I repaired an old Passat where the antifreeze was continuously decreasing due to a deteriorated cap seal. The owner even thought the engine was burning antifreeze. During inspection, I noticed white crystals around the radiator cap and obvious leakage from the connecting hoses. It's a good practice to check the cap seal during every maintenance service, and if you hear a hissing sound, shut off the engine immediately.
