What are the functions of the two water tanks in BMW?
2 Answers
BMW's two water tanks are divided into a compensation tank and an expansion tank, with specific functions as follows: 1. Volume expansion: Due to the thermal expansion and contraction characteristics, when the coolant heats up in the tank, its volume expands, requiring a place to store the expanded liquid. At this point, the other coolant tank comes into play. 2. Volume reduction: When the liquid in the tank cools down, its volume decreases, requiring the liquid from the other coolant tank to replenish it.
I've been driving a BMW for several years. The large reservoir mainly stores coolant to prevent the engine from overheating and exploding due to expansion. It has level markings indicating the coolant level, which should be checked during regular maintenance. Just top it up with dedicated coolant without exceeding the maximum line. The small reservoir plays a supporting role, helping to balance system pressure and recover excess liquid, commonly seen in some older models. Remember to check it during seasonal changes, especially after long summer trips when fluid loss is more likely. If you notice the level is low, wait until the engine cools down before adding coolant—opening the cap on a hot engine can cause burns. Change the antifreeze every two years to prevent rust and clogging in the pipes, saving money and ensuring safety.
