Cooling System: Description and Operation

Engine Cooling

CAUTION: All vehicles are filled with Motorcraft Premium Gold Engine Coolant. Always fill the cooling system with the same type of coolant that was drained from the system. Do not mix coolant types. Mixing coolant types may degrade the coolant's corrosion protection.

NOTE: If Cooling System Stop Leak Pellets are used, darkening of the Motorcraft Premium Gold Coolant from yellow to golden tan will occur.

The engine cooling system consists of the:
^ block heater.
^ fan blade and clutch.
^ fan shroud.
^ coolant expansion tank.
^ thermostat.
^ thermostat housing assembly (4.0L SOHC).
^ coolant pump.
^ radiator.
^ radiator cap.
^ radiator hose.
^ heater tube assembly (4.0L SOHC).

The radiator allows excess engine heat to be transferred to the air.

The coolant pump forces coolant to flow through the cooling system.

The thermostat is a control valve actuated by coolant temperature. When the thermostat is closed, coolant flow bypasses the radiator circuit and returns to the coolant pump. When the thermostat is opened, coolant is allowed to flow through the radiator circuit in order to transfer engine generated heat to the outside air.

The radiator cap serves as the location for filling the cooling system and provides for a controlled pressure in the cooling system. When the pressure reaches a predetermined level, a valve in the radiator cap opens to allow coolant to flow into the coolant expansion tank. As the engine cools, a valve in the radiator cap allows for coolant to flow from the coolant expansion tank back into the radiator.

The coolant expansion tank holds surplus coolant, allows for coolant expansion and replenishes coolant to the cooling system. It is equipped with a non-pressurized cap which allows coolant to be added to keep it filled to prescribed levels.

The electronically controlled fan clutch is controlled by the PCM based upon requests for airflow to cool the engine, transmission and A/C condenser. If no cooling is required, the electronics permit the fan to spin at a slower speed yielding improved fuel economy.

The optional block heater keeps the engine coolant warm during cold weather. The electrical heating element is installed in a core plug opening and uses a standard 110V electrical supply.

Engine coolant provides freeze protection, boil protection, cooling efficiency and corrosion protection to the engine and cooling components. In order to obtain these protections, the engine coolant must be maintained at the correct concentration and fluid level in the coolant expansion tank.

When adding engine coolant, use a 50/50 mixture of engine coolant and distilled water.

To maintain the integrity of the coolant and the cooling system:
^ add Motorcraft Premium Gold Engine Coolant. Do not mix coolant types.
^ do not add orange-colored Motorcraft Specialty Orange Engine Coolant. Mixing coolants may degrade the coolant's protection rating.
^ do not add alcohol or methanol or any engine coolants mixed with alcohol or methanol antifreeze. These can cause engine damage from overheating or freezing.
^ do not mix with recycled coolant. Use of such a coolant may harm the engine and cooling system components.
^ the addition of Cooling System Stop Leak Pellets darkens Motorcraft Premium Gold Engine Coolant from yellow to golden tan.