Description Reviews MINI Cooper S Aluminum Expansion Tank! We all know that the expansion tank is the weak point in the MINI Cooper S's Cooling system. Buy this aluminum tank and never have it fail again! This kit comes in flashy RED! It uses the OEM cap size so you know that it will pressurize correctly! All needed hardware is included for a quick install. You will need to top off the coolant so it might be a good idea to do a flush at the same time. Buy this kit that includes an aftermarket cap that works great and saves funds!