The coolant is a liquid substance which is being transported to the engine chamber so as to absorb the heat it generates. Normally, internal combustion engine produces heat every time they consume fuel or every time the vehicle runs. In the process of absorbing the heat, the coolant as a chemically formulated fluid expands. It usually expands and often times needed extra space where it can stay before it finally gets to the radiator to be re-cooled. Car manufacturers thought that the coolant should never be off-guarded while it is transferring heat and expanding so they put an alternative storage for it. This storage is what is called now as the expansion tank like your BMW expansion tank. Your BMW expansion tank is very useful to the coolant for the latter's temporary storage and safety. If in case the coolant expanded and there was no room for its excess quantity, the coolant might drip out the car and into the grounds. This will cause a shortage of coolant in the cooling system. Aside from that, your BMW expansion tank also helps in transporting the heated coolant to the radiator efficiently. With its function to the coolant, the expansion tank is therefore advised to be properly maintained and secured. Any damages in it will render poor service and of course low efficiency on the coolant. It may also cause the coolant to lose track of its systematic flow back to the radiator if in case the expansion tank got damaged. If in case you already experience manifestations of defective expansion tank have it checked by your auto mechanic. If he recommends that you get a replacement for it, you should only get what you have trusted before so purchase a new BMW expansion tank replacement. Our company website offers these replacement products in affordable prices and standard quality.