What Causes Coolant Leakage in BMW E66?
3 Answers
It is caused by a chemical reaction of the coolant, triggered by aluminum corrosion in the turbocharger intercooler or low-temperature coolant radiator. As a result, when the engine is cooled, opening the sealing cap on the low-temperature expansion tank may cause coolant to leak out as a secondary reaction. Introduction to Antifreeze: The full name should be antifreeze coolant, meaning a coolant with antifreeze properties. Antifreeze is a type of coolant containing special additives, primarily used in liquid-cooled engine cooling systems. It offers excellent performance in preventing freezing in winter, boiling in summer, and resisting scale and corrosion year-round. Hazards of Inferior Antifreeze: If the antifreeze is of poor quality or even counterfeit, it will not perform the functions of antifreeze. Coolant is typically prepared by mixing antifreeze with water in a specific ratio. Automobile manufacturers usually specify the mixing ratio for different low-temperature antifreeze grades in the user manual and also designate the type of antifreeze, which should not be mixed with other types.
My BMW E66 has had coolant leaks repaired several times. The most common issue is the aging water pump seal causing leaks, as plastic components tend to deteriorate over time. Other causes include loose hose connections or cracked plastic pipes, as the E66's materials can crack under high temperatures. A faulty radiator cap seal can also lead to pressure leaks. When the cylinder head gasket is damaged causing internal leaks, coolant mixing with engine oil becomes quite dangerous. It's crucial to inspect leaks promptly, otherwise engine overheating may cause cylinder scoring. You can perform simple checks like looking for pink fluid stains on the ground or rapid coolant level drops, but professional pressure testing at a repair shop is recommended for accurate diagnosis. For prevention, regular coolant changes can help extend component lifespan.
My E66 was leaking coolant the year before last, and it turned out to be a cracked plastic water pipe, likely due to high-temperature aging. The mechanic said water pump leaks are quite common, with seal wear being a major issue. Leakage at the cylinder head could be more troublesome, requiring a check for white smoke in the exhaust. Leaks shouldn't be ignored—insufficient coolant can lead to engine damage. I regularly check parking spots for wet stains, which are usually pink or green in color. If detected, repairs should be done promptly at a reliable repair shop. Regular maintenance of the cooling system is essential, including annual coolant changes to prevent component corrosion and extend lifespan.
