Cooling System: Description and Operation

COOLING SYSTEM
The cooling system consists of an engine cooling module, thermostat, coolant, and a water pump to circulate the coolant. The engine cooling module may consist of a radiator, electric fan motor, fan, shroud, coolant reserve system, transmission oil cooler, hoses, clamps, air condition condenser and transmission oil lines.
^ When the Engine is cold: The thermostat is closed; the cooling system has no flow through the radiator. The coolant flows through the engine, heater system and bypass.
^ When the Engine is warm: Thermostat is open; the cooling system has flow through radiator, engine, heater system and bypass.

Figure 1:

Coolant flow circuit is shown.
During any reassembly procedures all pipe fittings in water jacket, and waterbox require cleaning and application of thread sealant for entire length of threads.

ACCESSORY DRIVE BELTS

Figure 2:

If the engine is equipped with power steering or air conditioning, it will have 2 drive belts. One belt drives the generator, the other drives the Power Steering and Air Conditioning.

COOLANT RECOVERY SYSTEM (CRS)

Figure 3:

This system works in conjunction with the radiator pressure cap to utilize thermal expansion and contraction of the coolant to keep the coolant free of trapped air. The system provides space for expansion and contraction, and a convenient safe method for checking and adjusting the coolant level at atmospheric pressure without removing the pressure cap. It also provides some reserve coolant to compensate for minor leaks and evaporation or boiling losses. All vehicles are equipped with this system.
See Coolant Level Check, Deaeration and Radiator Cap information for operation and service.

ENGINE THERMOSTAT
The engine thermostat is located on the front of the engine (radiator side) in the thermostat housing engine outlet connector. The thermostat has an air bleed (vent) located in the flange and an O-ring for sealing incorporate on it. There is a relief in the thermostat housing/outlet connector for the O-ring.

WATER PUMP

Figure 4:

The water pump has a diecast aluminum body and housing with a stamped steel impeller. The water pump bolts directly to the block. Cylinder block to water pump sealing is provided by a rubber O-ring. The water pump is driven by the timing belt. Refer to Timing Components for component removal to access the water pump.

NOTE: The water pump on all models can be replaced without discharging the air conditioning system.

COOLANT
The cooling system is designed around the coolant. The coolant must accept heat from engine block metal and in the cylinder head area near the exhaust valves. Then coolant carries this heat to the radiator where the tube/fin assemblies of these components can give off the heat to the air.
Mopar(R) Antifreeze or the equivalent is recommended for optimum cooling performance and corrosion protection when mixed to a freeze point of -37° C (-35° F).

COOLANT REPLACEMENT
Refer to Maintenance for schedule.

COOLING SYSTEM PRESSURE CAP

Figure 5:

The cooling system is equipped with a pressure cap that releases pressure at some point within a range of 97-124 kPa (14-18 psi).
The system will operate at higher than atmospheric pressure, which raises the coolant boiling point, allowing increased radiator cooling capacity.

AUTOMATIC TRANSMISSION OIL COOLER

Figure 6:

Oil coolers are internal oil to coolant type, mounted in the radiator lower tank. Rubber oil lines feed the oil cooler and the automatic transmission. Use only approved transmission oil cooler hose. Since these are molded to fit space available, molded hoses are recommended. Tighten Oil Cooler Hose Clamps to 2 Nm (18 inch lbs.).

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

ENGINE BLOCK HEATER
The engine block heater is available as an optional accessory. The heater, operated by ordinary house current (110 Volt A.C.) through a power cord and connector behind the radiator grille, provides easier engine starting and faster warm-up when vehicle is operated in areas having extremely low temperatures.