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 consists of a radiator, electric fan and motor assembly, shroud, radiator pressure cap, Coolant Recovery System (CRS), hoses, and clamps.
^ When engine is cold the thermostat is closed. The cooling system has no flow through the radiator. The coolant flows through the engine, water pump, and heater.
^ When engine is warm the thermostat is full open. The coolant flows through the radiator, heater, and water pump.
The thermostat's 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 water (coolant) for heater operation. It does this by transferring heat from engine metal to coolant, moving this heated coolant to the radiator and heater core, and then transferring this heat to the ambient air.

Cooling System Operation (Flow Circuit):

The coolant flow circuit is shown in the illustration.

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 can give off the heat to the air.
Mopar 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.

COOLANT PERFORMANCE

Performance is measurable. For heat transfer, one pound of pure water absorbs 1 btu for each degree of temperature rise. This formula is altered when necessary additives to control boiling, freezing, and corrosion are added as follows:
^ Pure Water (1 btu) boils at 100°C (212°F) and freezes at 0°C (32°F).
^ 100 Percent ethylene glycol (0.7 btu) can cause an engine to run hot, cause detonation, and will freeze at -22°C (-8°F).
^ 50/50 Ethylene Glycol and Distilled Water (0.82 btu) is the recommended combination that provides a freeze point of -37°C (-35°F). The radiator, water pump, engine water jacket, radiator pressure cap, thermostat, temperature gauge, coolant sensor and heater are all designed for 50/50 ethylene glycol.
Where required, a 56 percent glycol and 44 percent water mixture will provide a freeze point of -46°C (-50°F).

NOTE: Richer mixtures cannot be measured with field equipment and can lead to problems associated with 100 percent glycol. If there is doubt that the coolant mixture is to rich for field equipment to measure, put a sample in a clean container. Add exactly the same amount of water and retest. If the coolant in the vehicle is 100% antifreeze, the diluted sample will read 50%. If the coolant in the vehicle was 70% antifreeze and 30% water, the diluted sample will read as 35%, etc.

SELECTION AND ADDITIVES

The use of aluminum cylinder heads, intake manifolds, and water pumps requires special corrosion protection. Mopar Antifreeze or the equivalent is recommended for optimum engine cooling and protection against corrosion when mixed to a freeze point of -37°C (-35°F) to -59°C (-50°F). If it looses color or becomes contaminated; drain, flush, and replace with fresh properly mixed solution.

CAUTION: Do not use well water, or suspect water supply in cooling system. A 50/50 ethylene glycol and distilled water mix is recommended.

COOLANT PRESSURE BOTTLE

Coolant Pressure Bottle:

This system works in conjunction with the coolant pressure bottle pressure cap to keep 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.
Refer to Coolant Level Check, and Coolant Pressure Cap for operation and service.

COOLANT PRESSURE CAP

Pressure Cap:

Pressure bottle is equipped with a pressure cap which release 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.

COOLING FAN MODULE

Cooling Fan Module:

The fan module is a combination of single, electric motor driven fan mounted to a one piece shroud. The fan system improves engine cooling in hot weather and severe driving conditions, while reducing fan noise and power consumption.

NOTE: The fan module is serviced as an assembly, the fan is not serviced separately.

COOLING FAN

All models use a single fan motor. The electric fan motor has two speeds, see Radiator Fan Control under Testing and Inspection for more information. The fan module includes a motor support and shroud.
The fan motor is controlled by the Powertrain Control Module (PCM). Attempts to reduce high temperature gauge reading by increasing engine speed, at the same vehicle speed, can increase high temperature.

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.

RADIATOR HOSES AND CLAMPS

WARNING: IF VEHICLE HAS BEEN RUN RECENTLY, WAIT 15 MINUTES BEFORE WORKING ON VEHICLE. RELIEVE PRESSURE BY PLACING A SHOP TOWEL OVER THE CAP AND WITHOUT PUSHING DOWN ROTATE IT COUNTERCLOCKWISE TO THE FIRST STOP ALLOW FLUIDS TO ESCAPE THROUGH THE OVERFLOW TUBE AND WHEN THE SYSTEM STOPS PUSHING OUT COOLANT AND STEAM AND THE PRESSURE DROPS CONTINUE SERVICE.
WARNING: CONSTANT TENSION HOSE CLAMPS ARE USED ON MOST COOLING SYSTEM HOSES. WHEN REMOVING OR INSTALLING, USE ONLY TOOLS DESIGNED FOR SERVICING THIS TYPE OF CLAMP ALWAYS WEAR SAFETY GLASSES WHEN SERVICING CONSTANT TENSION CLAMPS.

Spring Clamp Size Location:

CAUTION: A number or letter is stamped into the tongue, of constant tension clamps. If replacement is necessary, use only a original equipment clamp with matching number or letter.

Hose Clamp Tool:

The hose clamps are removed by using Special Tool 6094 or equivalent constant tension clamp pliers to compress the hose clamp.
A hardened, cracked, swollen or restricted hose should be replaced. Care should be taken not to damage radiator inlet and outlet when removing hoses.
Radiator hoses should be routed without any kinks and indexed as designed. The use of molded hoses is recommended.
Make sure hoses and connectors are clean and dry before installation. Do not lubricate hoses when installing.
Spring type hose clamps are used in all applications. If replacement is necessary, replace with the original Mopar equipment spring type clamp.

ENGINE OIL COOLER

Engine Oil Cooler:

Oil cooler is a external oil to air type, mounted in front of the radiator. Braided reinforced oil lines feed the oil cooler and the engine. Use only approved engine oil cooler lines. Tighten oil cooler line fittings to 47 Nm (35 ft. lbs.) at the oil filter adapter and 34 Nm (25 ft. lbs.) at the oil cooler.

THERMOSTAT

Thermostat Location:

The engine thermostat is located at the front of the engine, below the intake manifold. The thermostat is a moveable sleeve type. The outside sleeve moves up or down, directing coolant flow through the engine block or through the cast-in bypass passages back to the water pump.
The thermostat is unique in that the center does not open and close like a conventional thermostat. It works like a sliding sleeve. During warm up below 91°C (195°F) the thermostat is seated in the retracted position. This will allow the coolant to flow from the cast in water cross-over through the center of the thermostat, into the bypass passage, and back to the water pump. At 91°C (195°F) the thermostat begins to open (move downward), allowing coolant to flow from the water cross-over through both the bypass, and the radiator. At 104°C (219°F) the thermostat will fully seat downward, blocking the path to the bypass, allowing all coolant to flow through the radiator.

WATER PUMP

Water Pump And Gasket:

The pump has a cast aluminum body and a plastic impeller. It bolts directly to the timing chain case cover, using a gasket for sealing. It is driven by the back surface of the poly-V accessory drive belt.