Coolant Reservoir: Description and Operation

Expansion Tank




the plastic expansion tank for both models is located between the primary and secondary bulkheads. the MINI COOPER expansion tank is a non-pressurized type, it is only used to collect excess coolant due to heat expansion, and this coolant will be drawn back into the system as the coolant cools.
Both models use a pressure cap to pressurize the cooling system to 1.1 bar (16 psi) at which point the cap valve will lift to relieve pressure.

the MINI COOPER S is fitted with a conventional pressurized cap on the expansion tank.