Cooling System: Description and Operation

Engine Cooling

NOTICE: The engine cooling system is filled with Motorcraft Premium Gold Engine Coolant. Always fill the cooling system with the same type coolant that is present in the system. Do not mix coolant types. Failure to follow these instructions may result in engine or cooling system damage.

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

The engine cooling system consists of the following:

- Block heater (optional)
- Engine Coolant Temperature (ECT) sensor (4.0L engines)
- Cylinder Head Temperature (CHT) sensor (2.3L engines)
- Fan blade
- Fan clutch
- Fan shroud
- Fan shroud with electric fan (2.3L engines with A/C)
- Radiator
- Pressure cap
- Radiator coolant recovery reservoir (4.0L engines)
- Degas bottle (2.3L engines)
- Thermostat
- Coolant pump
- Radiator draincock

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

Radiator tanks cannot be repaired, install as an assembly.

For the 2.3L engine, the thermostat and housing must be serviced as an assembly.

The 2.3L engine uses a "cold side" thermostat. This means the thermostat is located at the lower radiator hose connection to the engine, where coolant enters the engine after being cooled by the radiator. During initial warm-up, the cooler coolant from the radiator will quickly close the thermostat after the warm coolant in the engine opens the thermostat slightly. The thermostat will open and close several times before the coolant coming from the radiator is warm enough to allow the thermostat to remain open. The engine must run much longer than a vehicle with a "hot side" thermostat before the thermostat remains fully opened.

The 4.0L engine use a typical "hot side" thermostat.

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

Do not add or mix Motorcraft Specialty Orange Engine Coolant. Mixing coolants may degrade the coolant's corrosion protection.
- Do not add alcohol, methanol, brine 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 coolants may harm the engine and cooling system components.

The optional block heater:

- electrical heating element is installed in the core plug opening.
- uses a standard 110V electrical supply

- keeps the engine coolant warm during cold weather.

Coolant Flow Diagram, 2.3L

NOTE: Black arrows indicate hot, white arrows indicate cold.











Coolant Flow Diagram 4.0L SOHC

NOTE: Black arrows indicate hot, white arrows indicate cold.