The task of the coolant pump, through a simple construction with only one rotating part, mostly with ball-bearings, is to keep the coolant in circulation under moderate pressure. This can easily amount to more than 100 liters/min at high RPM. In certain vehicles it's even driven electrically and is only switched on when required.
A ribbed wheel is driven by the engine. All that is needed is a positive connection through a wedge- or ribbed-belt or their rear side. The anti-clockwise rotating wheel (picture 4) slews the liqiud, which enters from the middle, to the wall of the round casing. This is where the outlet port, at a slight tangent, is found. Because it transports the coolant from the center outwards, it is also called a radial pump.
Formerly, the pumps were integrated into the cylinder-block, nowadays, they are sometimes situated in their own housing. They can be identified from the outside by the large diameter of the inlet and the outlet. Picture 2 shows a pump which is directly driven by a timing belt. The one shown in picture 3, is driven either by the rear or the face of the belt. In this case the belt-ridges will slowly be flattened out in the course of time.
The mechanical drive provided by the engine is in fact, not the best choice, because the greatest pumping requirements are often required at low revs. Therefore, electric pumps are more suitable, indeed, they still have difficulties with the required maximum performance. The simple solution of permanently running pumps fitted with a thermostat is, at least for smaller engines, more economical.
Constant-flow-pumps are in general, not self-priming, thus they will only
function if the cavity is completely filled with the medium to be pumped. 02/12