Cooling System: Description and Operation
2.0L Zetec-E Engine
2.0L SPI Engine
2.3L Engine
2.0L and 23L Engines (if equipped)
The thermostat allows rapid engine warm up by restricting engine coolant flow at lower operating temperatures. It also assists in maintaining engine operating temperatures between pre-determined limits.
WARNING: Disconnect the battery when working in the vicinity of the engine cooling fan. The fan is controlled by the engine management system and an increase in coolant temperature can cause the fan to operate even with the ignition in the OFF position. Failure to follow this instruction can result in personal injury.
The cooling fan(s) is mounted within a shroud behind the radiator.
Engine Coolant
WARNING: Engine coolant contains monoethylene glycol and other constituents, which are toxic if taken internally and can be absorbed into the skin after prolonged contact.
Engine coolant concentration should be checked through the neck of the expansion tank with a hydrometer. The acceptable range of specific gravity (sg) of correctly balanced fluids is between 11.10 and 11.20 lbs/gal, which represents an engine coolant concentration between 40 percent and 55 percent. If the concentration falls below 40 percent there is insufficient low temperature protection and the corrosion resistance will be inadequate. In such cases the concentration must be brought back to specification.
The engine coolant should not be mixed with other coolant types. For cooling system top off, only use coolant which meets specification.
Changing Coolant
WARNING: When releasing the system pressure, cover the expansion tank cap with a thick cloth to prevent the possibility of coolant scalding. Failure to follow this instruction can result in personal injury.
CAUTION: When draining the coolant or changing any cooling system components, it is imperative that no coolant comes into contact with the camshaft drive belt or accessory drive belt. If necessary, the belt should be removed. Contamination of the belt can result in belt failure.
NOTE: Providing the coolant has not been contaminated with other fluids or foreign matter, the robust corrosion resistance properties of this coolant means that it can be reused after changing an aluminum cooling system component, although the concentration should always be checked and maintained within specification.
This engine coolant should be changed after a period of 10 years or 150,000 miles, whichever occurs sooner. Refill with engine coolant mixed to the correct proportions.
Fail Safe Cooling (Zetec-E only)
The vehicle has a strategy built into the powertrain control module (PCM) that will control the engine if it starts to overheat.
Stage 1 of the strategy will commence if the engine starts to overheat. The cylinder head temperature (CHT) sensor transmits a signal to the PCM which then moves the temperature gauge pointer into the red zone.
If the engine is not switched off and the temperature continues to rise, the Powertrain Check Lamp is illuminated. This indicates to the driver that the engine is approaching critical limits and should be stopped. At this point DTC P1285 is set in the PCM which can be retrieved using a scan tool.
Stage 2 of the strategy will commence if the lamp and temperature gauge are ignored by the driver. The PCM will start to control the engine by cutting out two cylinders and restricting the RPM to below 3000 RPM. Simultaneously the malfunction indicator lamp (MIL) will be illuminated. This indicates that long term engine damage can occur and vehicle emissions will be affected. At this point DTC P1299 is set in the PCM which can be retrieved using a scan tool.
Air is then drawn into the deactivated cylinders. This helps to control the temperature of the engine internal components. The deactivated cylinders are alternated to allow even cooling of all the cylinders.
NOTE: If the driver is using a high percentage of throttle travel (for example, an overtaking maneuver) when the PCM starts engine deactivation (Stage 2), the deactivation will be delayed for 10 seconds.
NOTE: After 2-cylinder operation has begun, the engine will not revert to 4-cylinder operation, even if the temperature should fall, until the ignition is switched off and then on again.
NOTE: The malfunction indicator lamp can only be extinguished by using a diagnostic tool after the fault has been rectified and the DTC cleared.
Stage 3 of the strategy will commence if the engine temperature still continues to rise. This will result in the engine being totally disabled before major engine damage or seizure occurs. The Powertrain Check Lamp will begin to flash, indicating to the driver that the engine will be switched off after 30 seconds. This allows the driver time to choose a suitable parking place.
Run On Fan (ROF) system
The Run on fan system is designed to keep the engine cooling fans running to cool the underhood components after keying the engine off. The fans are kept running when heavy engine loads have occurred prior to keying the engine off.
The ROF system consists of an electronic ROF relay (high speed fan relay) and an air temperature switch. The ROF relay replaces the standard fan relay for high speed operation and has a built in electronic module to activate the fan output after the ignition has been switched off. The air temperature switch is located behind the engine beside the heated oxygen sensors (H02S) connectors.
During engine running and with the ignition switched on, the fan is controlled completely by the PCM in the same way as a non-ROF fan system. Dependent on the underhood temperature, the fans will keep running when the ignition is switched off. They remain running when the temperature is 96°C (204°F) ± 4.5°C (40°F) or above at the air temperature switch, until either the temperature decreases below 86°C (187°F) or the maximum run on time of 3 minutes has elapsed.