MGBs produced up to September 1976 used a mechanical engine-driven cooling fan, mounted on the water pump spindle and driven by belt from the crankshaft pulley. The fan type changed several times during production, and cars today may not be fitted with their original type, making visual identification the most reliable method when ordering a replacement. The earliest MGBs from 1962 were fitted with a three-blade metal fan, painted yellow, mounted on the water pump spindle. Only very early cars used an MGA-type six-blade metal fan, also painted yellow, but this was short-lived.
The three-blade metal fan remained the standard fitment on home market and most export cars through to 1974. From the start of MkII production in 1967, a six-blade metal fan was fitted to cars with 18GF engines built to the North American specification, and this type was also used on non-North American cars fitted with the automatic gearbox.
In December 1972, North American cars changed to a seven-blade one-piece plastic fan, and this was also adopted on automatic gearbox cars regardless of market. The three-blade metal fan continued on all other cars.
In March 1974, the fan type was finally commonised across the range, with an alternative seven-blade plastic fan incorporating metal inserts being introduced on all cars. However, even after this commonisation, the original three-blade metal fan was reinstated on cars for Switzerland from October 1974 to comply with local noise regulations.
Pulleys & Fan Belts
With the introduction of the rubber bumper models in September 1974, the crankshaft pulley diameter was increased and a smaller fan pulley adopted, along with a new fan belt and alternator adjusting link. These changes affect the pulley and belt specifications but not the fan blade type itself. The fan belt drives both the water pump and the alternator (or dynamo on very early cars) and should be checked regularly for correct tension, cracking, and glazing. A slipping or broken fan belt will cause rapid overheating as both the water circulation and the fan airflow are lost simultaneously.
Replacement fan belts should be matched to the correct pulley combination for the engine fitted. The mechanical cooling fan was discontinued from September 1976 onwards, when it was replaced by a thermostatically controlled electric fan as part of the wider cooling system redesign.