A method of controlling temperature of an engine (120, 220) of a vehicle and of one or more auxiliary components of the vehicle, the engine (120, 220) and the one or more auxiliary components being coupled to a cooling system (101, 201) disposed about said engine (120, 220) and said one or more auxiliary components, and the method comprising: (i) monitoring one or more parameters of the engine (120, 220) including the temperature of the engine (120, 220); and (ii) selecting a cooling mode for the cooling system (101, 201), wherein said selecting a cooling mode is carried out at least in part by a control unit and wherein each of a plurality of cooling modes is defined by: (i) a flow rate at which coolant is output by a pump (122, 222) of the cooling system (101, 201); and (ii) the route(s) about the cooling system (101, 201) open to the flow of coolant, which route(s) is determined in dependence upon whether one or more valve means (140a, 140b, 340, 342) comprised within the cooling system (101, 201) is closed or open, wherein said control unit is configured and arranged to actively and passively control said one or more valve means (140a, 140b, 340, 342) to passively and/or actively open or close one or more fluid conduits comprised within the cooling system (101, 201), thereby controlling the route(s) available for the flow of coolant about the cooling system (101, 201) and thereby activating the selected cooling mode; the valve means is arranged to move between open and closed positions responsive to the temperature within the valve means; passively controlling the valve mean comprises allowing the coolant to heat the valve means thereby causing the valve means to move between an open position and a closed position; and actively controlling the valve means comprises controlling a heating means to electrically heat the valve means thereby causing the valve means to move between an open position and a closed position wherein the method further comprises monitoring requirements of one or more auxiliary components of the vehicle of the vehicle and in that the selection of the cooling mode by said control unit is performed in dependence on the monitored parameters of the engine and the monitored requirements of the one or more auxiliary components; and wherein selecting the cooling mode comprises selecting from: (i) a first series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is zero; (ii) a second series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is above zero and equal to or less than a low flow rate; (iii) a third series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is greater than said low flow rate and is below a maximum flow rate; and a fourth series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is a maximum flow rate. (i) monitoring one or more parameters of the engine (120, 220) including the temperature of the engine (120, 220); and (ii) selecting a cooling mode for the cooling system (101, 201), (i) a flow rate at which coolant is output by a pump (122, 222) of the cooling system (101, 201); and (ii) the route(s) about the cooling system (101, 201) open to the flow of coolant, which route(s) is determined in dependence upon whether one or more valve means (140a, 140b, 340, 342) comprised within the cooling system (101, 201) is closed or open, (i) a first series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is zero; (ii) a second series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is above zero and equal to or less than a low flow rate; (iii) a third series of cooling modes wherein the flow rate of the coolant output by the pump (122, 222) is greater than said low flow rate and is below a maximum flow rate; and