Download The cooling system components include the: block heater (optional) cylinder head temperature sensor fan blade, fan motor and fan shroud assembly radiator pressure relief cap degas bottle radiator draincock water pump oil cooler (optional) water thermostat The water thermostat: controls the engine coolant temperature. allows quicker engine warm-up. The degas bottle: provides a location for system fill. contains coolant expansion and system pressurization. provides air separation during operation. replenishes the engine coolant to the system. The fan blade draws air through the radiator to help cool the engine coolant. The fan motor: operates only when the engine is running. will not operate when the engine is off. The engine coolant flows: from the lower radiator hose to the water pump. from the water pump to the engine block and the cylinder heads. A closed water thermostat returns the engine coolant to the water pump. An open water thermostat allows the engine coolant to flow to the radiator.