Abstract: An improved unified cooling system for an internal combustion engine that generally includes a cylinder head and a cylinder block, in which the cylinder head and cylinder block are maintained at different operating temperatures despite using only a single coolant pump. The coolant pump pumps fresh coolant through the cylinder head and cylinder block. Coolant valves, which may be thermostatic valves or electrically actuable proportional valves, lie downstream of the cylinder head and cylinder block and individually control the amount of coolant flowing through the cylinder head and cylinder block so as to maintain a lower operating temperature for the cylinder head than for the cylinder block. Coolant is directed, in various configurations, through any or all of an oil cooler, a heat exchanger for a heater for a vehicle interior, and a coolant radiator, before being directed back to the coolant pump.