A compound cycle engine comprising: an internal combustion engine; a compressor having compressed air delivered to the internal combustion engine; a cooling system (38;138) comprising: a fluid circuit having an intercooler, a main cooler and a precooler, the intercooler configured for receiving coolant and configured for heat exchange relation between the coolant and engine compressed air, the main cooler configured for receiving the coolant from the intercooler and the internal combustion engine, and configured for selectively delivering a first portion of the coolant from the main cooler to the precooler, the precooler configured to deliver a flow of the coolant to the intercooler, and the main cooler and the precooler configured for cooling the coolant by heat exchange with at least one cooling flow; and a bypass valve in fluid communication with the fluid circuit downstream of the main cooler and upstream of the precooler and the intercooler relative to a flow direction of the first portion of the coolant to selectively bypass the precooler and to provide direct fluid communication from the main cooler to the intercooler; a duct receiving the main cooler and the precooler, the duct including a blower to circulate the at least one cooling flow in heat exchange relation with the coolant in the main cooler and the precooler; and an oil cooler disposed in the duct and in fluid communication with oil from the internal combustion engine, the oil cooler configured for heat exchange relation between the oil and the at least one cooling flow to cool the oil. an internal combustion engine; a compressor having compressed air delivered to the internal combustion engine; a cooling system (38;138) comprising: a fluid circuit having an intercooler, a main cooler and a precooler, the intercooler configured for receiving coolant and configured for heat exchange relation between the coolant and engine compressed air, the main cooler configured for receiving the coolant from the intercooler and the internal combustion engine, and configured for selectively delivering a first portion of the coolant from the main cooler to the precooler, the precooler configured to deliver a flow of the coolant to the intercooler, and the main cooler and the precooler configured for cooling the coolant by heat exchange with at least one cooling flow; and a bypass valve in fluid communication with the fluid circuit downstream of the main cooler and upstream of the precooler and the intercooler relative to a flow direction of the first portion of the coolant to selectively bypass the precooler and to provide direct fluid communication from the main cooler to the intercooler; a fluid circuit having an intercooler, a main cooler and a precooler, the intercooler configured for receiving coolant and configured for heat exchange relation between the coolant and engine compressed air, the main cooler configured for receiving the coolant from the intercooler and the internal combustion engine, and configured for selectively delivering a first portion of the coolant from the main cooler to the precooler, the precooler configured to deliver a flow of the coolant to the intercooler, and the main cooler and the precooler configured for cooling the coolant by heat exchange with at least one cooling flow; and a bypass valve in fluid communication with the fluid circuit downstream of the main cooler and upstream of the precooler and the intercooler relative to a flow direction of the first portion of the coolant to selectively bypass the precooler and to provide direct fluid communication from the main cooler to the intercooler; a duct receiving the main cooler and the precooler, the duct including a blower to circulate the at least one cooling flow in heat exchange relation with the coolant in the main cooler and the precooler; and an oil cooler disposed in the duct and in fluid communication with oil from the internal combustion engine, the oil cooler configured for heat exchange relation between the oil and the at least one cooling flow to cool the oil.