Cooling system and internal combustion engine with the cooling system

A cooling system, in which any bubble is not transferred to the water pump (coolant pumping means), and thereby the efficiency of the water pump is prevented from lowering, so that the cooling performance is enhanced, and an internal combustion engine provided with the cooling system are to be provided. The interior of a water outlet (coolant distributing means) 3 mounted on a cylinder head (internal combustion engine) 1 is divided by a partition wall 3b to form a feeding chamber 3c to feed the coolant introduced from the cylinder head 1 to the first path A provided with a radiator, and a receiving chamber 3d composing the second path B to receive the coolant returned from a heater core. Between the receiving chamber 3d and the feeding chamber 3c is formed a channel (bubble introducing portion) 3e making one of both chambers communicate with the other. As a result, bubbles in the coolant running through the second path B are introduced into the feeding chamber 3c through the channel 3e and removed from the radiator.