A cooling system is provided having a first heat exchanger configured to remove heat from at least a portion of a first fluid and a second heat exchanger configured to remove heat from a portion of a second fluid. The second heat exchanger is located downstream of the first heat exchanger relative to the flow of air passing through the first heat exchanger so that a substantial portion of the air passing through the first heat exchanger also passes through the second heat exchanger. The cooling system also has a valve located to regulate the flow of the second fluid through the second heat exchanger. The cooling system further has a controller configured to actuate the valve to restrict the flow of the second fluid through the second heat exchanger when the first heat exchanger is removing heat from the first fluid.