Water Pump Original Equipment Small Bore Engine

It's warmer here than in the UK. This higher capacity water pump moves more coolant than the stock one, and is better quality. GWP132 has by-pass hose take off and is made especially for the small bore engines. The impeller in these aluminum bodied pumps is long lasting cast iron, not stamped steel as in many aftermarket pumps. Use of a high capacity water pump helps to reduce cavitation in the water jacket, particularly at high RPM, as well as circulating a greater volume of coolant. Further reduction of cavitation is achieved by using a large diameter water pump pulley CAM6408 as originally fitted to the Cooper S and reintroduced on the A-Plus engines. It is necessary to check clearance between the large pulley and the head; if a lot of material has been machined from the head face it may foul the pulley. Small bore engines with 12G940 heads can't use CAM6408 and it is necessary to modify the top edge of the high capacity water pump or the 12G940 head will rest on the pump and not seal properly; modify for at least 1/16" gap.