The water pump circulates coolant through engine, head and radiator, driven by the fan belt from the crankshaft. Pump specifications differ between engine types, particularly the change from A-series to A+, the introduction of bypass and non-bypass variants on 1275cc Cooper, non-Cooper and SPi cars, and the polyvee belt arrangement on MPi models from 1997 requiring a specific pump. Water pump impellers corrode over time, reducing efficiency. Modern alloy-bodied pumps are available as a direct replacement for the original cast iron units, offering reduced weight without loss of durability.
Thermostats
The thermostat controls coolant flow from the engine, remaining closed during warm-up and opening progressively at its rated temperature. Available in 74°C, 82°C and 88°C settings. A thermostat with a built-in jiggle valve is recommended for older engines, allowing trapped air to pass during filling rather than creating an air lock.
MGOC Spares Range
The MGOC Spares Classic Mini water pump and thermostat range covers water pumps for all A-series and A+ variants, thermostat housings, thermostats in all temperature ratings, housing gaskets, fan belts and all associated fixings.