Patent ID: 7798108

Claim:
A water-jacket structure for a water-cooled internal combustion engine, comprising: a cylinder block having at least one cylinder bore and a cylinder block water jacket surrounding the cylinder bore; and a cylinder head joined to an upper surface of the cylinder block and having a cylinder head water jacket, a cooling water passage being formed to cause cooling water to flow from the cylinder block water jacket into the cylinder head water jacket; wherein: a gasket is interposed between the cylinder block and the cylinder head, said gasket being formed with an upper connecting opening which opens at an upper part of the cylinder block water jacket and connects to the cylinder head water jacket, the cylinder block has an outer side wall of the cylinder block water jacket, the outer side wall partly bulging outward to form a bulging part defining a bulged space therein, the bulged space is separated by a partition member from the cylinder block water jacket to define in the bulged space a lower connecting passage which opens into a lower part of the cylinder block water jacket and extends upward from the lower part of the cylinder block water jacket in parallel disposition with the cylinder block water jacket, and the cylinder block water jacket and the lower connecting passage are in communication with said upper connecting opening thereabove and with the cylinder head water jacket.