Cooling System: Description and Operation

Engine Cooling
The cooling system components include the:
- block heater (optional)
- cylinder head temperature sensor
- fan blade, fan motor and fan shroud assembly
- radiator
- pressure relief cap
- degas bottle
- radiator draincock
- water pump
- oil cooler (optional)
- water thermostat
The water thermostat:
- controls the engine coolant temperature.
- allows quicker engine warm-up.
The degas bottle:
- provides a location for system fill.
- contains coolant expansion and system pressurization.
- provides air separation during operation.
- replenishes the engine coolant to the system.
The fan blade draws air through the radiator to help cool the engine coolant.
The fan motor:
- operates only when the engine is running.
- will not operate when the engine is off.
The engine coolant flows:
- from the lower radiator hose to the water pump.
- from the water pump to the engine block and the cylinder heads.
A closed water thermostat returns the engine coolant to the water pump. An open water thermostat allows the engine coolant to flow to the radiator.
Unsatisfactory coolant materials:
- Alcohol-type antifreeze does not provide adequate water pump lubrication.
- has lower boiling point
- reduced antifreeze protection
- Alkaline brine solutions will cause serious engine cooling system damage.
The cylinder head temperature sensor provides a signal to the temperature gauge.
- will invoke fail-safe cooling.
The optional block heater:
- electrical heating element is installed in the block cooling jacket.
- uses a standard 110V (220V in Europe) electrical supply
- keeps the engine coolant warm during cold weather.
The auxiliary water pump (3.9L only):
- provides heater coolant flow boost.
- has a secondary function of providing engine-off cooling.