DESCRIPTION - COOLING SYSTEM
The cooling system consists of an engine cooling module, thermostat, coolant, a water pump to circulate the coolant. The engine cooling module may consist of a radiator, electric fan motor, shroud, radiator pressure cap, coolant reserve system, transmission oil cooler and lines, hoses, clamps, and air conditioning condenser.
OPERATION
The primary purpose of a cooling system 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 performance and cooling for automatic transmission oil. 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.
The coolant flow circuit is shown. (Scheme 10)
Scheme 10
Scheme 11
Scheme 12
Scheme 13
Scheme 14
Scheme 15
Scheme 16
Scheme 17
DESCRIPTION
| CAUTION | Use of Propylene Glycol based coolants is not recommended, as they provide less freeze protection and less corrosion protection. DO NOT mix coolant types. If coolant other than Mopar(R) Antifreeze/Coolant, 5 Year/100,000 Mile Formula or equivalent is added, the mixed coolant will have a reduced service schedule. |
The use of aluminum cylinder heads, and water pumps requires special corrosion protection. Mopar(R) Antifreeze/Coolant, 5 Year/100,000 Mile Formula or equivalent ethylene glycol based coolant with corrosion inhibitors (called HOAT, for Hybrid Organic Additive Technology) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% Ethylene Glycol and 50% distilled water to obtain a freeze point of -37°C (-35°F). If it loses color or becomes contaminated, drain, flush, and replace with fresh properly mixed coolant solution. Mixing of coolants other than specified (non-HOAT), will reduce the 5 year/100,000 mile corrosion protection.
| CAUTION | The power cord must be secured in its retainer clips, and not positioned so it could contact linkages or exhaust manifolds and become damaged. |
The heater is mounted in a core hole (in place of a core hole plug) in the engine block, with the heating element immersed in coolant. (Scheme 18) The engine block heater is available as an optional accessory. The heater is operated by ordinary house current (110 Volt A.C.) through a power cord and connector behind the radiator grille.
Scheme 18
The block heater element is submerged in the cooling system's coolant. When electrical power (110 volt A.C.) is applied to the element, it creates heat. This heat is transferred to the engine coolant. This provides easier engine starting and faster warm-up when vehicle is operated in areas having extremely low temperatures.
The engine coolant temperature (ECT) sensor threads into the rear of the cylinder head, next to the camshaft position sensor. (Scheme 19) New sensors have sealant applied to the threads.
The ECT Sensor is a Negative Thermal Coefficient (NTC) Sensor. The resistance of the ECT Sensor changes as coolant temperature changes. This results in different input voltages to the PCM. The PCM also uses the ECT Sensor input to operate the radiator cooling fan(s), and send a message over the PCI bus to the instrument cluster for temperature gauge operation.
Scheme 19
The ECT sensor provides an input to the PCM. As temperature increases, resistance of the sensor decreases. As coolant temperature varies, the ECT sensor resistance changes resulting in a different voltage value at the PCM ECT sensor signal circuit. The ECT sensor provides input for various PCM operations. The PCM uses the input to control air/fuel mixture, timing, and radiator fan on/off times. The PCM uses ECT sensor input to send messages over the PCI bus for temperature gauge operation.
The engine thermostat is located on the left front side (radiator side) of the cylinder head in the thermostat housing/engine outlet connector. (Scheme 20) The thermostat has an air bleed (vent) located in the flange and a "O"-ring for sealing incorporate on it. A relief in the thermostat housing/outlet connector is provided for the "O"- ring.
Scheme 20
The engine thermostat is a wax pellet driven, reverse poppet choke type. It is designed to provide the fastest warm up possible by preventing leakage through it and to guarantee a minimum engine operating temperature of 88 to 93°C (192 to 199°F). Also, the thermostat will automatically reach wide open, to accommodate unrestricted flow to the radiator as temperature of the coolant rises in hot weather to around 104°C (220°F). Above this temperature the coolant temperature is controlled by the radiator, fan, and ambient temperature-not the thermostat.
A thermostats 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 performance. It does this by transferring heat from engine metal and automatic transmission oil cooler (if equipped) to coolant, moving this heated coolant to the heater core and radiator, and then transferring this heat to the ambient air.
DESCRIPTION - HOSE CLAMPS
The cooling system utilizes spring type hose clamps. If a spring type clamp replacement is necessary, replace with the original Mopar(R) equipment spring type clamp.
| 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. (Scheme 21) |
Scheme 21
The spring type hose clamp applies constant tension on a hose connection. To remove a spring type hose clamp, only use constant tension clamp pliers (Special Tool 8495) designed to compress the hose clamp.
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 coolant within operating temperatures.
The radiator has an aluminum core with plastic tanks. Although stronger than brass, plastic tanks are subject to damage by impact. Always handle radiator with care.
The radiator functions as a heat exchanger, using air flow across the exterior of the radiator tubes. This heat is then transferred from the coolant and into the passing air.
The cooling system is equipped with a pressure cap that releases built up pressure, maintaining a range of 97-124 kPa (14-18 psi).
There is also a vent valve in the center of the cap. This valve also opens when coolant is cooling and contracting, allowing coolant to return to radiator from coolant reserve/recovery system container by vacuum through connecting hose. If valve is stuck shut, the radiator hoses will be collapsed on cool down. Clean the vent valve to ensure proper sealing when boiling point is reached. see scheme 23
Scheme 22
The pressure cap allows the cooling system to operate at higher than atmospheric pressure. The higher pressure raises the coolant boiling point; this allows increased radiator cooling capacity.
The gasket in the cap seals the filler neck, so that vacuum can be maintained, allowing coolant to be drawn back into the radiator from the reserve container.
The radiator fan is a single speed electric motor driven fan. The radiator fan assembly components includes an electric motor, a fan blade, and a support shroud that is attached to the radiator. Each component of the fan assembly can be serviced separately.
Depending on Engine/Transmission combination, the vehicle may be equipped with a single fan (Scheme 24) or a dual fan (Scheme 25)
Note. Vehicles equipped with dual fans, each fan blade is different from the other.
Scheme 23
Scheme 24
Radiator fan control operation is accomplished two ways. The fan will always run when the air conditioning compressor clutch is engaged. In addition to this control, the fan is turned on by the temperature of the coolant which is sensed by the coolant temperature sensor which sends the message to the Powertrain Control Module (PCM). The PCM turns on the through a fan relay by grounding the relay's coil. The fan relay is located in the Power Distribution Center (PDC). ( (Scheme 26) and see scheme 30 ). Refer to the label beneath the PDC cover for location of fan relay.
Scheme 25
Scheme 26
The PCM will actuate the fan relay whenever the A/C clutch is engaged regardless of coolant temperature and vehicle speed. If the A/C clutch is not engaged, the PCM will actuate the fan relay when the coolant temperature reaches approximately (97° C) 207° F and turns off the fan relay when the coolant temperature drops to approximately (94°C) 201° F. The fan relay is also turned off when the vehicle speed is above approximately 100 Km/h (62 MPH). For wiring diagrams of the fan circuit, refer to SYSTEM WIRING DIAGRAMS information.
If the radiator fan is inoperative or a Diagnostic Trouble Code (DTC) related to fan control has been set, refer to Appropriate Diagnostic Information for complete diagnostic procedures.
Note. The water pump on all models can be replaced without discharging the air conditioning system.
The water pump has a die-cast aluminum body and housing with a stamped steel impeller. The water pump bolts directly to the cylinder block and is driven by the timing belt. (Scheme 28) Cylinder block to water pump sealing is provided by a rubber "O" ring.
Scheme 27
The water pump is the heart of the cooling system. The coolant is pumped through the engine block, cylinder head, heater core, and radiator.
The water pump inlet tube connects the water pump housing to the radiator lower hose and heater return hose. This plastic tube is sealed by an O-ring and held in place by fasteners to the block. (Scheme 30)
Scheme 28
The accessory drive consist of two Poly-V type drive belts. (Scheme 31) One belt drives the generator, the other drives the power steering pump and air conditioning compressor (if equipped). The power steering/air conditioning belt is tensioned by an automatically controlled belt tensioner. The generator belt is manually tensioned using an adjusting bolt and a locking nut.
Scheme 29
The accessory drive belts form the link between the engine crankshaft and the engine driven accessories.
Scheme 30
Scheme 31
Scheme 32
- Using a 17 mm wrench, rotate belt tensioner clockwise until belt can be removed from power steering pump pulley. (Scheme 33) Gently, release spring tension on tensioner.
- Remove the drive belt. (Scheme 34)
Scheme 33
Scheme 34
- Remove power steering pump/air conditioning compressor drive belt.
- Loosen generator locking nut. see scheme 44
- Raise vehicle on hoist.
- Remove accessory drive belt splash shield. see scheme 45
- Loosen generator pivot bolt. see scheme 44
- Loosen generator adjusting bolt until generator belt can be removed. see scheme 44
- Remove generator belt.
The automatic belt tensioner maintains proper tension on the power steering and air conditioning belt. The tensioner is serviced with the engine mount bracket assembly. (Scheme 37) The tensioner pulley can be serviced separately.
Scheme 35
The transmission oil cooler is an oil to coolant type, mounted in the radiator lower tank. (Scheme 38) Rubber hoses connect the oil cooler and the automatic transmission. Use only approved transmission oil cooler hoses that are molded to fit the applicable vehicle. The transmission cooler is serviced with the radiator.
Scheme 36
As oil flows through the cooler, heat from the oil is transferred to the coolant.
The transmission oil cooling circuit uses special aggressive fittings for the transmission oil cooler hoses. Whenever a transmission oil cooler hose is removed from a transmission fitting (at transmission), it must be cut off flush with the fitting, and a service splice kit must be used upon reassembly. Refer to instructions provided with splice kit. Whenever a transmission oil cooler hose is removed from a transmission oil cooler fitting (at radiator), it must be replaced with a new hose. Removing the hose from the aggressive fitting will scrape material from inside the hose making the hose larger. Failure to replace the hose or install a service splice kit will result in transmission oil leaks.
When hose clamp replacement is necessary, replace with constant tension spring type hose clamps. Always use proper hose clamp pliers on clamps. Use of improper hose clamp pliers may bend hose clamps out-of-round resulting in transmission oil leaks.
Scheme 37
Scheme 38
- While holding tension on hose clamps with pliers, move clamps off the fitting location of hose.
- Disconnect hoses from cooler. see scheme 52 Disconnect hoses from transmission fittings. see scheme 53
- Remove cooler hoses.