Cooling System: Description and Operation
COOLING SYSTEMThe cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible. It also maintains normal operating temperature and prevents overheating.
The cooling system also provides a means of heating the passenger compartment and cooling the automatic transmission fluid (if equipped). The cooling system is pressurized and uses a centrifugal water pump to circulate coolant throughout the system.
An optional factory installed maximum duty cooling package is available on most models. This package will provide additional cooling capacity for vehicles used under extreme conditions such as trailer towing in high ambient temperatures.
COOLING SYSTEM COMPONENTS
The cooling system consists of:
^ A radiator
^ Cooling fan (electrical for 2.5L 4-cylinder engine-mechanical for 3.9L/5.2L/5.9L engines)
^ Thermal viscous fan drive-3.9L/5.2L/5.9L Engines
^ Fan shroud
^ Radiator pressure cap
^ Thermostat
^ Coolant reserve/overflow system
^ Transmission oil cooler (if equipped with an automatic transmission)
^ Coolant
^ Water pump
^ Hoses and hose clamps
COOLING SYSTEM CIRCULATION
Engine Cooling System -2.5L Engine- Typical:
Engine Cooling System -3.9L/5.2L/5.9L Engines- Typical:
For cooling system routings refer to illustrations above.
COOLANT RESERVE/OVERFLOW SYSTEM
Coolant Reserve/Overflow System:
The coolant reserve/overflow system works in conjunction with the radiator pressure cap. It utilizes thermal expansion and contraction of coolant to keep coolant free of trapped air. It provides a volume for expansion and contraction of coolant. It also provides a convenient and safe method for checking coolant level and adjusting level at atmospheric pressure. This is done without removing the radiator pressure cap. The system also provides some reserve coolant to the radiator to cover minor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the cooling system of both the radiator and engine. Coolant will then be drawn from the coolant tank and returned to a proper level in the radiator.
COOLANT
The cooling system is designed around the coolant. Coolant flows through the engine water jacket absorbing heat produced during engine operation. The coolant carries the heat to radiator and heater core. Here it is transferred to the ambient air passing through the radiator and heater core fins. The coolant also removes heat from the automatic transmission fluid in vehicles equipped with an automatic transmission.
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. DO NOT OPEN A COOLING SYSTEM WHEN THE ENGINE IS AT RUNNING TEMPERATURE, PERSONAL INJURY CAN RESULT. AVOID RADIATOR COOLING FAN WHEN ENGINE COMPARTMENT RELATED SERVICE IS PERFORMED, PERSONAL INJURY CAN RESULT.
CAUTION: Do not use straight antifreeze as engine coolant, inadequate engine running temperatures can result. Do not operate vehicle without proper concentration of recommended ethylene glycol coolant, high running temperatures and cooling system corrosion can result.
The cooling system factory fill is a mixture of 50% Ethylene Glycol based antifreeze and 50% water. Using a suitable hydrometer, measure antifreeze concentration in the radiator when the engine is cool. If the cooling system has recently been serviced, allow coolant to circulate for at least 20 minutes before taking hydrometer reading. Properly mixed coolant will protect the cooling system to -37*C (-35°F). If the freeze protection is above -28*C (-20°F), drain enough coolant from the cooling system to allow room to add antifreeze to achieve adequate protection.
Chrysler Corporation recommends Mopar(r) Antifreeze/Coolant or a high quality, ethylene glycol base antifreeze/coolant, with a silicate inhibitor.
RADIATOR PRESSURE CAP
Radiators are equipped with a pressure cap, which releases pressure at some point within a range of 97 - 124 kPa (14 - 18 psi). The pressure relief point (in pounds) is engraved on top of cap.
Radiator Pressure Cap And Filler Neck:
The cooling system will operate at pressures slightly above atmospheric pressure. This results in a higher coolant boiling point allowing increased radiator cooling capacity. The cap contains a spring-loaded pressure relief valve that opens when system pressure reaches release range of 97 - 124 kPa (14 - 18 psi).
A vent valve in the center of cap allows a small coolant flow through cap when coolant is below boiling temperature. The valve is completely closed when boiling point is reached. As the coolant cools, it contracts and creates a vacuum in the cooling system. This causes the vacuum valve to open and coolant in the reserve/overflow tank to be drawn through its connecting hose into radiator. If the vacuum valve is stuck shut, the radiator hoses will collapse on cooldown. Clean the vent valve.
A rubber gasket seals radiator filler neck to prevent leakage. This is done to keep system under pressure. It also maintains vacuum during coolant cool-down allowing coolant to return from reserve/ overflow tank.
COOLING SYSTEM FAN-2.5L ENGINE
Electric Fan Motor -2.5L Engine- Typical:
Power Distribution Center (PDC):
Models equipped with 2.5L engine have an electrical cooling fan. The fan is electrically controlled by the Powertrain Control Module (PCM) through the fan control relay. This relay is located in the Power Distribution Center (PDC). For the location of the relay within the PDC, refer to label on PDC cover.
The PCM regulates fan operation based on input from the engine coolant temperature sensor and vehicle speed.
The fan is not energized during engine cranking regardless of the electrical input from the engine coolant temperature sensor. However, if engine operating conditions warrant fan engagement, the fan will run once engine starts.
The fan is energized whenever the engine is running and the air conditioning compressor clutch is engaged.
When the air conditioning compressor clutch is disengaged, the fan operates at vehicle speeds above 40 mph. This is done if engine coolant temperature is above 110° (230°F). The same is true for vehicles that are not equipped with air conditioning. The fan will turn off when coolant temperature drops to 104°C (220°F). At speeds below 40 mph, the fan turns on when coolant temperature reaches 99°C (210°F) and turns off when coolant temperature drops to 93°C (200°F).
THERMOSTAT
Thermostat -3.9L/5.2L/5.9L Engines:
On 3.9L and 5.2L/5.9L engines, the thermostat is located beneath the thermostat housing at front of intake manifold. This thermostat has an air bleed notch.
RADIATOR
The radiators used in the 2.5L models are of the down-flow type (vertical tubes) and have plastic tanks. The radiators used in the 3.9L/5.2L/5.9L models are of the cross-flow type (horizontal tubes) and have plastic side tanks. The radiator supplies sufficient heat transfer to cool engine.
CAUTION: Although plastic radiator tanks are stronger than brass, they are more susceptible to damage from impact or excessive hose clamp torque.
Radiator Components-Typical:
In the event of damage to a plastic radiator tank, replacement tanks and O-ring seals are available through the parts department. Tank repair should be performed by qualified personnel using proper equipment.
WATER PUMP
The water pump on all models can be removed without discharging the air conditioning system (if equipped).
3.9L/5.2L/5.9L ENGINES
The water pump on 3.9L and 5.2L/5.9L engines is bolted directly to the engine timing chain case/cover.
A gasket is used as a seal between the water pump and timing chain case/cover.
If water pump is replaced because of bearing/shaft damage, or leaking shaft seal, the mechanical cooling fan assembly should also be inspected. Inspect for fatigue cracks, loose blades, or loose rivets that could have resulted from excessive vibration. Replace fan if any of these conditions are found. Also check condition of the thermal Viscous Fan Drive. Refer to Fan Clutch.
WATER PUMP BYPASS-3.9/5.2L/5.9L ENGINES
Water Pump Bypass Hose -3.9L/5.2L/5.9L Engines:
A water pump bypass hose is used between the intake manifold and water pump on all 3.9/5.2L/5.9L engines. To test for leaks, refer to Testing and Inspection.
ACCESSORY DRIVE BELT TENSION
Belt tension is adjusted at the power steering pump bracket and idler pulley assembly. For belt replacement and tension specifications, refer to Engine, Drive Belts, Mounts, Brackets and Accessories removal and installation.
Automatic Belt Tensioner -3.9L/5.2L/5.9L Engine:
It is not necessary to adjust belt tension on 3.9L W-6) or 5.2L/5.9L (V-8) engine. The engine is equipped with an automatic belt tensioner. The tensioner maintains correct belt tension at all times. For other tensioner information and removal/ installation procedures, refer to Drive Belt Tensioner in Drive Belts, Mounts, Brackets and Accessories under Engine. Due to use of this belt tensioner, do not attempt to use a belt tension gauge on 3.9L/5.2L/5.9L engines.