Description Reviews MINI Cooper S Expansion Tank! These fail from time to time on R52 or R53 MINI Cooper S's. Very early on they all failed right at the seam and that unit was a clear milky white color. By early 2003 they had a fix for the problem; they created a new tank that is still milky in but more of tan in color. They also updated the cap on the inside and the seal. You can tell by the bright blue seal inside of it. Nowadays we see some leak from the seam and some from the cap. We do sell the cap by itself if needed. This is a brand new OEM design and comes with the new updated cap. Comes with a 2 year unlimited miles warranty from MINI! Want more under bonnet bling with a permanent solution? Try the tank from Forge.