A motor vehicle engine cooling system includes a fluid flow control device having first and second fluid inlets and first and second fluid outlets. The first fluid inlet is arranged to be connected to a cylinder head coolant outlet of the engine and the second fluid inlet is arranged to be coupled to a cylinder block coolant outlet of the engine. The first fluid outlet is coupled to a radiator bypass conduit of the cooling system and the second fluid outlet is coupled to a radiator conduit of the cooling system and arranged to direct to flow through a radiator of the system. The device comprises a radiator outlet valve operable to control a flow of fluid out from the device through the second outlet, the valve having a closure member operable between an open position and a closed position responsive to a temperature of coolant flowing through the device, wherein when the closure member transitions from the closed position to the open position the closure member is arranged to be displaced in a direction downstream of a direction of flow of coolant through the second outlet.