shown of the v type four cylinder four stroke cycle internal combustion engine 1 via a hose not shown the aforementioned coolant outlet port 36 is connected to the coolant passage 50 see fig3 of the v type four cylinder four stroke cycle internal combustion engine 1 as shown in fig4 the coolant pump cover 41 is formed in such a manner that the side edge 53 of the front plate portion 52 of the coolant pump cover 41 can be brought into intimate contact with the side wall 51 of the set back recess 34 of the front cover 8 a communication passage 56 is defined by the wall 54 and the side wall 51 of the set back recess of the front cover 8 and the front plate portion 52 and the side wall 55 of the coolant pump cover 41 since the embodiment shown in the figure is constructed as described above the following operation is performed when the v type internal combustion engine 1 starts and the crankshaft 11 rotates the pump rotor of the coolant pump 42 is rotated since the coolant is cold during startup the thermostat not shown closes the water passage leading to the inlet pipe joint 48 and opens the water passage leading to the bypass pipe joint 49 therefore coolant is drawn from the coolant passage 50 into the v type internal combustion engine 1 via the hose and the bypass pipe joint 49 into the coolant passage 44 of the coolant pump 42 after being pressurized coolant flows through the coolant passage 44 and the coolant outlet port 36 into the coolant passage 50 accordingly localized.