Engine cooling circuit and method of cooling an engine

A flow control valve assembly for an engine cooling circuit comprises first inlet and outlet ports 142,144 for coolant flow from/to an engine 110 and second inlet and outlet ports 148,146 for coolant flow from/to a radiator 120. The first outlet port and second inlet port are above the first inlet port in use. A flow diverter portion 140D has a first configuration where coolant flows from the first inlet port to the first outlet port, and second configuration where coolant flows from the first inlet port to the second outlet port and from the second inlet port to the first outlet port. An upper region of the valve assembly may have a degas tank inlet 149. When the valve assembly is operated in the first configuration, gas bubbles entrained in coolant leaking past 'F2' the flow diverter portion can rise through the degas tank inlet to a degas tank 170. A method of cooling an engine comprises controlling a flow control valve to cause coolant fluid to circulate through the engine but substantially not through a radiator and a degas tank, or to cause coolant fluid to circulate through the engine, the radiator and the degas tank.