Engine Cooling - System Operation and Component Description

System Operation

The cooling system components include the:

• radiator
• cooling fan motor and shroud
• degas bottle
• coolant pump
• thermostat housing
• block heater (if equipped)

Engine coolant flows primarily from the engine to the radiator circuit and back to the coolant pump. Coolant is sent from the coolant pump through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core with coolant. The coolant pump, operated by engine rotation through the accessory drive belt, circulates the coolant. The coolant 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 flows through the radiator circuit to transfer engine-generated heat to the outside air.

The 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 quickly closes the thermostat after the warm coolant in the engine opens the thermostat slightly. The thermostat opens and closes 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 thermostat monitor is a function of the PCM and is designed to verify correct thermostat operation. The monitor executes once per drive cycle and has a monitor run duration of 300-800 seconds. If a malfunction occurs, DTC P0125 or P0128 sets, and the MIL illuminates.

The degas bottle holds surplus coolant and removes air from the cooling system. It also allows for coolant expansion and system pressurization, replenishes coolant to the cooling system and serves as the location for service fill.

Engine coolant provides freeze protection, boil protection, corrosion protection and cooling efficiency to the engine and cooling components. In order to obtain these protections, maintain the engine coolant at the correct concentration and fluid level in the degas bottle.

When adding or topping off the engine coolant:

• measure the coolant concentration in the vehicle using Coolant/Battery Refractometer 300-ROB75240 or equivalent.
• determine the concentration desired based on the vehicle duty cycle of extreme hot or cold operating conditions.
• add/top off or adjust the coolant as follows:
  • for concentrations measured 48/52 to 50/50 (equates to a freeze point between -34°C (-30°F) and -37°C (-34°F)), use Motorcraft® Orange Antifreeze/Coolant Prediluted to maintain a coolant concentration in this same range (freeze protection down to -37°C (-34°F).
  • for all other concentrations, use Motorcraft® Orange Antifreeze/Coolant Concentrated and/or distilled water to get to the desired concentration.
    Refer to: Cooling System Draining and Vacuum Filling (303-03A Engine Cooling - 1.6L Duratec-16V Ti-VCT (88kW/120PS) - Sigma, General Procedures).
    

When refilling the engine coolant after a flush procedure, use a mixture of Motorcraft® Orange Antifreeze/Coolant Concentrated and distilled water to get to the desired concentration.

To maintain the integrity of the coolant and the cooling system:

• Add Motorcraft® Orange Antifreeze/Coolant.
• Do not add or mix with any other engine coolant. Mixing coolants degrades the coolant 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.
• Ford Motor Company does NOT recommend the use of recycled engine coolant in vehicles originally equipped with Motorcraft® Orange Antifreeze/Coolant since a Ford-approved recycling process is not yet available.

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