1.  Field of the Invention
The present invention relates to a cooling system for an engine, and more particularly to a cooling system having means to control the flow of a cooling medium. 
2.  Description of the Related Art
In general, a cooling system for an engine is designed to provide the most suitable cooling condition for generating high power or producing good gas mileage. 
For example, a favorable flow of a cooling water (cooling medium) is shown in FIG.  3.  There, the cooling water flows from one side 72 of a cylinder block 71 to which is fixed an intake manifold (not shown), to the other side 73 of the cylinder block 71 to which is fixed an exhaust manifold (not shown).  Thus, the intake manifold is colder than the exhaust manifold, so that intake air is cooled and the filling efficiency of the intake air into the cylinder is improved. 
Referring to FIG.  4, a housing 81 of a conventional water pump (not shown) is sealed to a suction cover 82 of the water pump via a gasket 87.  The suction cover 82 is sealed to a cylinder block 83 of an engine via a seal member 84.  A cooling water passage 85 is formed between the housing 81 and the suction cover 82.  A cooling water jacket 86 is formed in the cylinder block 83. 
In the FIG.  4, an inlet 86a of the water jacket 86 is offset from a center 83a of the cylinder block 83 to achieve the above-mentioned most suitable cooling condition.  However, cooling water will flow in two directions as shown by arrows X,Y. Additionally, the inlet is not offset in a conventional cylinder block, so that the above-mentioned cooling system cannot be applied to conventional cylinder block. 
Therefore, the cooling arrangement is not suitable.