Cooling System: Description and Operation

OPERATION
The engine cooling system operates as follows:
1. Coolant flows through the radiator tubes and is cooled by air passing over the cooling fins assisted by the cooling fan motor and fan blades.
2. Coolant is then circulated from the radiator outlet tank (8054) through the water pump (8501) and into the cylinder block (6010) to complete the circuit.

PRESSURE RELIEF CAP
1. Coolant expands as the temperature and pressure rise in the system.
2. When the limiting system working pressure is reached, the pressure relief valve in the radiator cap (8100) is lifted from its seat and allows coolant to flow through the radiator filler neck and the radiator overflow hose (8075) into the radiator coolant recovery reservoir (8A080).
3. When the system temperature and pressure drop, the coolant contracts in volume and the pressure in the radiator (8005) is reduced.
4. The coolant in the radiator coolant recovery reservoir will then flow back into the radiator through the vacuum relief in the radiator cap. The radiator cap has a rubber seal on the underside to prevent leakage.

COMPONENTS
The engine cooling system consists of:
- radiator(8005).
- water pump (8501).
- engine cooling fan motor (8K621) and fan blade (8600) which are activated by the constant control relay module (CCRM).
- radiator coolant recovery reservoir (8A080), located beside the radiator and aids in maintaining the correct volume of engine coolant mixture in the cooling system.

COOLING FAN OPERATION

NOTE: Cooling fan motor will not cycle with the A/C clutch (2884) ON when vehicle speed is over 72 km/h (45 mph) and coolant temperature is below 104�C (220�F). The cooling fan motor will then automatically shut OFF.

The cooling fan motor is mounted within a fan shroud (8146) behind the radiator (8005). The constant control relay module (CCRM)(12B581) actuates the cooling fan motor:
when the coolant reaches a specified temperature.
when the engine reaches a specified speed.
when the A/C clutch is activated (if equipped), and vehicle speed is below 72 km/h (45 mph).

COOLANT RECOVERY SYSTEM

WARNING: NEVER REMOVE THE RADIATOR CAP (8100) UNDER ANY CONDITIONS WHILE THE ENGINE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN DAMAGE TO THE COOLING SYSTEM OR ENGINE AND/OR PERSONAL INJURY. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE RADIATOR (8005), USE EXTREME CARE WHEN REMOVING THE RADIATOR CAP FROM A HOT RADIATOR. WAIT UNTIL THE ENGINE HAS COOLED, THEN WRAP A THICK CLOTH AROUND THE RADIATOR CAP AND TURN IT SLOWLY TO THE FIRST STOP. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN CERTAIN ALL THE PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE RADIATOR CAP (STILL WITH A CLOTH), TURN AND REMOVE IT.

This system uses:
^ A 110 kPa (16 psi) radiator cap.
^ A radiator coolant recovery reservoir (8A080) and hose.
The advantages of the system are:
^ Extra coolant is carried in the radiator coolant recovery reservoir.
^ Any air bubbles trapped in the cooling system are vented in the radiator coolant recovery reservoir rather than causing excessive aeration of the coolant.

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.