Cooling System: Description and Operation

Cooling System
The cooling system consists of an engine cooling module, pressure cap, coolant bottle, thermostat (inlet), coolant, and a water pump to circulate the coolant. The engine cooling module consist of a radiator, air conditioning condenser, electric fan motor and shroud.
^ When Engine is cold: thermostat is closed, cooling system has no flow through the radiator. The coolant flows through the engine heater core, coolant bottle and an internal engine bypass.
^ When Engine is warm: Thermostat is open, coolant flows through the radiator, heater core, coolant bottle and bypass.
The cooling systems primary purpose is to maintain engine temperature in a range that will provide satisfactory engine performance and emission levels under all expected driving conditions. It also provides hot coolant for heater, and cooling for automatic transmission fluid. It does this by transferring heat from engine metal to coolant, moving this heated coolant to the radiator, and then transferring this heat to the ambient air.

Cooling System Flow:

Coolant flow circuit is shown.

Accessory Drive Belts
The accessory drive system utilizes two different belts. A conventional V-belt drives the air conditioning compressor and a Poly-V belt drives the generator, and power steering pump.

Coolant Pressure Bottle

Coolant Pressure Bottle:

This bottle keeps the coolant free of trapped air. It provides a volume for expansion and contraction and provides a convenient and safe method for checking coolant level and adjusting level at atmospheric pressure. It also provides some reserve coolant to cover minor leaks and evaporation or boiling losses.

Engine Thermostat

Thermostat And Housing:

The thermostat is located on the lower left side of engine, near the front. The thermostat is on the inlet side of the water pump. The thermostat has an air bleed located in the thermostat flange.

Water Pump

Water Pump:

The pump has a plastic swept vane impeller. The water pump body bolts directly to the right rear timing belt cover, using an O-ring gasket for pump to cover sealing. The pump is driven by the engine timing belt.

Coolant

CAUTION: Use of Propylene Glycol based coolants is not recommended as they provide less freeze protection and less corrosion protection.

The cooling system is designed around the coolant. The coolant must accept heat from engine metal, in the cylinder head area near the exhaust valves and engine block. The coolant carries heat to the radiator where the tube/fin radiator can transfer the heat to the air.
The use of aluminum cylinder heads, intake manifolds, and water pumps requires special corrosion protection. Mopar Antifreeze or the equivalent ethylene glycol base antifreeze with a silicate inhibitor is recommended for best engine cooling without corrosion, when mixed only to a freeze point of -37°C (-35°F) to -59°C (-50°F). If it loses color or becomes contaminated, drain, flush, and replace with fresh properly mixed solution.

WARNING: ANTIFREEZE IS AN ETHYLENE GLYCOL BASE COOLANT AND IS HARMFUL IF SWALLOWED OR INHALED. IF SWALLOWED, DRINK TWO GLASSES OF WATER AND INDUCE VOMITING. IF INHALED, MOVE TO FRESH AIR AREA. SEEK MEDICAL ATTENTION IMMEDIATELY. DO NOT STORE IN OPEN OR UNMARKED CONTAINERS. WASH SKIN AND CLOTHING THOROUGHLY AFTER COMING IN CONTACT WITH ETHYLENE GLYCOL. KEEP OUT OF REACH OF CHILDREN. DISPOSE OF GLYCOL BASE COOLANT PROPERLY, CONTACT YOUR DEALER OR GOVERNMENT AGENCY FOR LOCATION OF COLLECTION CENTER IN YOUR AREA. 130 NOT OPEN A COOLING SYSTEM WHEN THE ENGINE IS AT OPERATING TEMPERATURE OR HOT UNDER PRESSURE, PERSONAL INJURY CAN RESULT AVOID RADIATOR COOLING FAN WHEN ENGINE COMPARTMENT RELATED SERVICE IS PERFORMED, PERSONAL INJURY CAN RESULT.

Radiator
The radiator is a cross-flow type (horizontal tubes) with design features that provide greater strength as well as sufficient heat transfer capabilities to keep the engine satisfactorily cooled.

CAUTION: Plastic tanks, while stronger than brass are subject to damage by impact, such as wrenches, or heat from torch.

Coolant Bottle Pressure Cap

Pressure Cap And Bottle:

The Coolant bottle is equipped with a pressure cap which releases pressure at some point within a range of 117 kPa ± 7 kPa (17 psi ± 1 psi).
The system will operate at higher than atmospheric pressure which raises the coolant boiling point thus allowing increased radiator cooling capacity.
There is a spring-loaded vent valve in the center of the cap that allows the system to pressurize and depressurize without creating a vacuum. If the valve is stuck open, coolant will escape to the overflow hose. There is also a gasket in the cap to seal to the top of the filler neck.

CAUTION: Use only the pressure cap specified for this vehicle. Use of other pressure caps can lead to coolant loss and overheating.

Fan Module

Fan Module:

The fan module consist of a single cooling fan, with a two speed electric motor that is supported by a one piece shroud. The fan module is secured to the radiator by fasteners with clips and at lower attachment points. The fan is controlled by the Powertrain Control Module (PCM) which energizes the fan relay.

Automatic Transmission Oil Cooler

Transmission Oil Cooling Module:

The transmission oil cooler is an external oil-to-air type. The oil cooler has a single speed "pusher" fan that is electric motor driven and attached to the oil cooler support bracket. The transmission oil cooling module is mounted to the rear frame rail of the vehicle. Fan operation is controlled by the Powertrain Control Module (PCM) which energizes the fan relay.