The MGA uses a mechanical engine-driven cooling fan bolted to the water pump pulley, drawing air through the radiator at all engine speeds. The fan is a six-blade pressed steel unit, driven by the V-belt that also turns the water pump and dynamo from the crankshaft pulley. The same six-blade fan was carried forward onto the earliest MGB three-bearing engines before MG revised the MGB fan design.
Fan Specification
The fan specification was consistent across all pushrod MGA variants, the same six-blade fan fits the 1500, 1600, and Mk II. The fan is bolted to the water pump shaft using four bolts and spring washers, with the fan extension riding on the pulley face to position the fan correctly in relation to the radiator cowl. The correct fan-to-radiator clearance is important, too close risks the fan striking the cowl or radiator core if the engine mounts are worn, while too far away reduces cooling efficiency.
Replacement fans, bolts, and spring washers are available as individual parts or together.
Twin Cam Cooling Fan
The Twin Cam cooling system differs from the pushrod arrangement. The Twin Cam radiator sits further forward in the chassis to clear the longer engine, and the system uses a separate remote header tank on the left-hand side of the engine bay rather than the integral header tank on the pushrod radiator. At engine number 272 (September 1958) the Twin Cam dynamo pulley was changed to a smaller diameter to increase dynamo speed and improve charging rate, and the fan belt length was reduced accordingly, the fan itself was unchanged, but the fan belt specification differs between early and post-272 Twin Cam engines.
Fan Belt Adjustment
Correct fan belt tension is critical. A loose belt slips, causing the water pump to underperform and the dynamo to undercharge, while an over-tight belt accelerates bearing wear in the water pump and dynamo. The belt is tensioned by loosening the dynamo mounting bolts and pivoting the dynamo on its bracket until the correct tension is achieved, approximately half an inch of deflection under firm thumb pressure at the midpoint of the longest belt run is the standard BMC specification. The fan belt should be inspected at every service for signs of cracking, glazing, or fraying, and replaced as a matter of routine maintenance rather than waiting for failure, a broken belt will quickly stop coolant circulation and can cause overheating before the driver notices the temperature rising.
Electric Fan Conversions
Electric cooling fan conversions replace the mechanical fan with a thermostatically controlled electric unit. The advantages are threefold: the fan provides full airflow regardless of engine RPM, which is particularly valuable in slow traffic where mechanical fan airflow is minimal; it eliminates the parasitic drag of the mechanical fan at cruising speed, reducing under-bonnet noise and freeing a small amount of engine power; and the fan runs only when required, allowing a faster warm-up from cold. MGOC stocks the Kenlowe electric fan kit as the MGA-specific option, with a separate thermo-switch kit available for fitting into the top hose where the kit's own thermostat location is not preferred. Revotec electric fan kits are also available through the wider Accessories range for owners who prefer that brand.
Ordering Notes
When ordering fan components, the key distinction is pushrod versus Twin Cam. The six-blade mechanical fan is the same across all pushrod variants; the fan bolts, spring washers, and fan belt complete the assembly. For Twin Cam cars, confirm the engine number when ordering the fan belt, the correct belt length differs between engines built before and after engine number 272. For electric fan conversion, specify pushrod or Twin Cam so the correct mounting hardware is supplied.