Radium Coolant Expansion Tank Remote locationThe Radium remote mounted coolant header tank is commonly required for custom Lotus applications such as engine swaps, turbocharger kits, etc. where the OEM expansion tank is no longer in an ideal location. The main tank is a 2 piece design constructed of CNC 6061 billet aluminum, as shown below. The two halves are bolted together along with a CNC billet aluminum cap receiver which mates to any standard 32mm "Type A" style pressure cap. Coolant header