6.7 LITER. lower. MAIN COOLING SYSTEM. Oil cooler line. PartQualifier: engine cooler lower. Flexible Hose that is part of the engine cooling system. Hoses carries permanent coolant, or antifreeze, throughout the engine, heater, and radiator. AND Amplifier; tube. Engine Coolant. Oil Cooler Line. Radiator Coolant. Sunvisor. Water Outlet.