Cooling System: Description and Operation

DESCRIPTION
The engine coolant:
1. Flows through the radiator tubes and is cooled by air passing over the cooling fins (assisted by the cooling fans as necessary).
2. It is then circulated from the radiator outlet tank (8054) through the lower radiator hose (8286), which provides a T-joint to the radiator coolant recovery reservoir (8A080) which is pressurized to continuously separate the air from the cooling system.
3. Flows from the radiator coolant recovery reservoir through the engine, heater core (18476) and water pump (8501), then returns to the radiator (8005) through the water hose connection (8592) and upper radiator hose (8260).

COMPONENTS
The engine cooling system includes the following:
^ Mechanical cooling fan blade with viscous fan clutch.
^ Auxiliary electric cooling fan motor and fan blade (8600), activated by the variable control relay module.
^ Heater water hoses (18472).
^ Oil cooler(6A642).
^ Radiator (8005).
^ Radiator coolant recovery reservoir (8A080) located beside the radiator, aids in maintaining the correct volume of engine coolant.
^ Upper radiator hose (8260) and lower radiator hose (8286).
^ Water pump (8501).
^ Water thermostat (8575).

COOLANT RECOVERY SYSTEM

NOTE: When the water thermostat (8575) is closed, there is no flow through the degas bottle.

Trapped air in the cooling system must be removed. A pressurized radiant degas bottle system is used which continuously separates the air from the cooling system. The degas bottle serves as the location for:
- Service fill.
- Coolant expansion during warm-up.
- System pressurization from the pressure relief cap.
- Air separation during operation.

When the water thermostat is open, coolant flows through the small hose from the top of the radiator outlet tank to the degas bottle. The degas bottle separates any trapped air from the coolant and replenishes the system through its radiator coolant recovery hose.

BLOCK HEATER
The optional block heater (6A051) is designed to keep the engine coolant warm during cold weather to aid in cold starting. It consists of:
1. Electrical heating element installed in one of the core plug openings in the cylinder block (6010).
2. Electrical cable which plugs into a standard 110-volt AC electrical outlet.
Refer to Engine for repair procedures.

ELECTRICAL SYSTEM

NOTE: With A/C ON, the auxiliary electric cooling fan motor will run continuously. Auxiliary electric cooling fan motor will not cycle ON and OFF with A/C clutch (2884). An exception to this is when vehicle speed is over 72 km/h (45 mph) and coolant temperature is below 104°C (220°F). The auxiliary electric cooling fan motor will then automatically shut OFF.

The auxiliary electric cooling fan motor is mounted within a fan shroud (8146) behind the radiator (8005). The powertrain control module (PCM)(12A650) actuates the auxiliary electric cooling fan motor when:
^ The coolant reaches a specified temperature.
^ The engine is below a specified speed and the A/C clutch is activated.