Most modern liquid cooled engines employ a pump. The pump ensures a more positive circulation of the coolant and is necessary for engines of high power output and complicated cylinder block and head construction which would not receive adequate cooling from thermo-syphon system.
Many goods vehicles are fitted with tilt cabs which require a low-height coolant radiator to give adequate clear Angeles when swiveling the cap. A header tank mounted on the back of the cab is normally employed on those vehicles.
Many larger engine employ this type of pump in the cooling system. Circulation of the coolant is much faster as this pump operates with a higher delivery pressure being caused by the different pump construction and the effects of centrifugal force on the coolant. This type of pump is usually driven by gears from the engine timing gears.
A centrifugal pump consists of a casing which houses an impeller and drive spindle. Coolant enters the casing at the centre of the impeller and is forced radially outwards along the blades by centrifugal force into the stationary casing where it is directed to the pump outlet. The impeller spindle is carried on a self-aligning ball bearing which permits a slight misalignment between the pump and its driving member. The seal is a spring loaded carbon gland with the carbon ring fixed
in the casing, and the spherical seating rotates with impeller shaft. In the later design of this pump, the carbon gland seal has been superseded by the unit seal.
Also check: Impeller Pump and how its works