The water pump, cooling fan, thermostat, and fan belt are engine-mounted cooling components that differ significantly between the 1275cc and 1500cc, and within the 1275cc range the water pump and pulley arrangement varies depending on the engine prefix and the cooling system layout, vertical-flow or crossflow.
1275cc Cooling Components
Two water pumps were used across 1275cc production, the earlier pump fitted to early engines running with the vertical-flow radiator, and a revised pump adopted on later engines when the crossflow radiator was introduced, care being needed when fitting the crossflow pump to an earlier engine as the fan blade-to-block clearance must be checked to avoid contact, with the gasket and pulley supplied separately. The cooling fan is a six-blade item throughout production, but the material changed, early cars using a six-blade metal fan, now no longer available as a new part, and later cars adopting a six-blade plastic fan offering improved durability and reduced risk of radiator damage if a blade fails, the plastic fan being the standard replacement option. Three fan belt lengths were used across 1275cc production, the correct length determined by whether the car has a dynamo or alternator and the pulley diameter fitted, and a bypass hose connects the water pump housing to the thermostat area, maintaining coolant circulation through the engine when the thermostat is closed.
1500 Cooling Components
The 1500 water pump is completely different from either 1275cc pump, bolting to a separate water pump housing on the front of the block via studs with its own gasket, the mounting pattern, impeller, and housing all being unique to the Triumph engine so that no 1275cc pump can be substituted. The 1500 uses a seven-blade plastic fan specific to this engine, originally an off-white colour from the factory with modern aftermarket replacements typically yellow, shared in design with the Triumph Spitfire 1500, and the 1500 fan belt is unique to this engine. The thermostat on the 1500 sits in a separate housing bolted to the water pump assembly, with a dedicated filler cap providing the coolant filling point, and the housing gasket is specific to the 1500.
Thermostats
The thermostat controls coolant flow between the engine and radiator, opening progressively as the engine warms to maintain the correct operating temperature, and is available in 74°C, 82°C, and 88°C ratings, with 82°C the standard UK fitment, the 88°C suiting cars that spend extended periods in traffic or are used for towing and the 74°C sometimes preferred for competition use. On the 1275cc, the thermostat housing differs between vertical-flow and crossflow cooling systems, the vertical-flow housing outlet pointing upward while the crossflow housing directs the outlet to the left-hand side of the radiator, so confirming the cooling system layout fitted to the car is essential when ordering the correct thermostat housing and gasket.