an action of circulating the coolant in the coolant passageway 1 at an ordinary time is described an action performed at the time of the operation in which the coolant is injected into the coolant passageway 1 will be described in detail incidentally the discharging of the coolant from the coolant passageway 1 is carried out by a worker removing a drain bolt not shown provided on a lower portion of the radiator and also removing the radiator cap 34 at this time a drain bolt not shown provided on the cylinder block 152 of the engine 150 may also be removed furthermore injection of the coolant into the coolant passageway 1 is carried out via the filling port that is opened by removing the radiator cap 34 next with reference to fig3 and 4 a coolant circulating action in the cooler apparatus 100 according to an embodiment of the invention will be described action during cold state during warm up firstly immediately after the engine 150 is started the temperature of the coolant is low so that the thermostat 4 is in the closed valve state as shown in fig3 then as the electric water pump 2 is driven the coolant is caused to flow through the electric water pump 2 the passageway 11 the block side water jacket.