Engine Cooling System & Automatic Transmission Cooling System: Overview Jeep Compass I

COOLING-DESCRIPTION-GAS ENGINE

The 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 consists

1. Radiator
2. Coolant
3. Electric cooling Fans
4. Water pump
5. Thermostat
6. Charge air cooler (Turbocharged vehicles only)
7. In-radiator Power steering oil cooler (Turbocharged vehicles only)
8. Hoses and clamps
9. Transmission oil cooler
10. Coolant pressure bottle/overflow system

Scheme 10

The water pump draws coolant from the radiator and delivers it to the engine block. The coolant travels through the engine block into the cylinder head. Coolant exits the engine at the thermostat. If the coolant temperature is less than 87°C (189°F) the thermostat directs all of the coolant back to the water pump. If the coolant temperature is between 87°C (189°F) and 102°C (216°F) the thermostat is in the mix mode and directs the coolant to the radiator and the water pump. If the coolant is greater than 102°C (216°F), the thermostat directs all of the coolant to the radiator.

The thermostat also feeds excess coolant and bleeds air from the system through a hose leading to the coolant reservoir. The reservoir returns coolant to the inlet side of the water pump. A port and hose at the rear of the engine block provides coolant to the heater core. This coolant is returned to the engine at the intake side of the water pump.

The oil cooler receives coolant directly from the engine block. A hose returns this coolant to the inlet side of the water pump.

OPERATION-GAS ENGINE

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.

1. When the Engine is cold and both the primary and secondary thermostats are closed. The coolant will circulate through the engine, heater system, and the bypass. The cooling system has no flow through the radiator
2. As the engine warms up, the primary thermostat will start to open at 82 °C (179 °F). Coolant will start to flow through the radiator and the internal transmission cooler. The primary thermostat will fully open at 95 °C (203 °F).
3. The secondary thermostat will start to open at 95 °C (203 °F). This will increase the coolant flow through the cylinder block and cylinder head and the radiator. The secondary thermostat will fully open at 110 °C (230 °F).

DESCRIPTION

The automatic belt tensioner maintains proper tension on the accessory drive belt. The tensioner pulley can be serviced separately.

COOLANT-OPERATION

Coolant flows through the engine block absorbing the heat from the engine, then flows to the radiator where the cooling fins in the radiator transfers the heat from the coolant to the atmosphere. During cold weather the ethylene-glycol or coolant prevents water present in the cooling system from freezing within temperatures indicated by mixture ratio of coolant to water.

DESCRIPTION-GAS ENGINE

The coolant recovery system consists of a coolant recovery container mounted to the RH inner wheel housing, a vent hose for the coolant recovery container, a hose connecting the container to the radiator neck, and a pressure cap.

OPERATION-DIESEL

The location of the container allows any air or vapor exceeding the pressure/vent cap rating to escape through the cap. Coolant flows through the container at all times during engine operation whether the engine is cold or at normal operating temperature. The coolant container is equipped with a pressure/vent cap. For more information. See DESCRIPTION .

The system works in conjunction with the cooling system 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. Also, the system provides a convenient and 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.

Scheme 11

1. Partially drain cooling system using the draincock only. See «STANDARD PROCEDURE»(ref-304343-S02124729692008110700000) . Drain system below level of the coolant recovery pressure container.
2. Disconnect return hose (1) at coolant recovery pressure container (3).
3. Remove coolant recovery pressure container bolt.
4. Lift container up at disconnect coolant hose (2) from bottom of coolant container.
5. Remove coolant recovery container from engine compartment.

Scheme 12

1. Siphon coolant from coolant recovery container.
2. Remove return hose (5) from upper radiator hose tee (3).
3. Remove coolant recovery bottle mount bolt (2).
4. Disengage coolant recovery container (6) from washer reservoir bottle (4).
5. Remove coolant recovery container and drain.

OPERATION

The block heater element is inserted into a bore in the engine block. When electrical power (110 volt A.C.) is applied to the element, it creates heat. This heat is transferred to the aluminum engine block. This provides easier engine starting and faster warm-up when vehicle is operated in areas having extremely low temperatures.

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.

Scheme 13

1. Disconnect negative battery cable.
2. Remove engine cover. Refer to «REMOVAL»(ref-304329-S27147758722008110700000) - 2.0L. Refer to «REMOVAL»(ref-304330-S22459581352008110700000) - 2.4L.
3. Partially drain coolant system below pressurized coolant recovery container. See «STANDARD PROCEDURE»(ref-304343-S02124729692008110700000) .
4. Unplug coolant temperature sensor electrical connector. NOTE: Capture any residual coolant that may flow.
5. Remove coolant temperature sensor (5).

When the Engine is cold and both the primary and secondary thermostats are closed. The coolant will circulate through the engine, heater system, and the bypass. The cooling system has no flow through the radiator

As the engine warms up, the primary thermostat will start to open at 82 °C ( 179 °F). Coolant will start to flow through the radiator oil cooler and transmission cooler. Coolant will flow through the transmission oil cooler only when the primary thermostat is fully open. The primary thermostat will fully open at 95 °C (203 °F).

The secondary thermostat will start to open at 95 °C (203 °F). This will increase the coolant flow through the cylinder block and cylinder head and the radiator. The secondary thermostat will fully open at 110 °C (230 °F).

If the thermostat is stuck open or allows coolant leakage through it, the engine will not operate at the proper temperature for obtaining engine fuel efficiency, performance and emissions levels. If this condition occurs, a diagnostic trouble code will be set and a MIL light will be turned on. Refer to appropriate engine ELECTRICAL DIAGNOSTICS article for further information and diagnostics provided.

OPERATION-DIESEL ENGINE

A vent valve in the center of the cap will remain shut as long as the cooling system is pressurized. As the coolant cools, it contracts and creates a vacuum in cooling system. This causes the vacuum valve to open and coolant in reserve/overflow tank to be drawn through connecting hose into radiator. If the vacuum valve is stuck shut, or overflow hose is kinked, radiator hoses will collapse on cool-down.

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 secondary gasket in the cap seals the filler neck and the primary gasket seals the cooling system so that vacuum can be maintained, allowing coolant to be drawn back into the radiator from the reserve container.

A vent valve in the center of the cap will remain shut as long as the cooling system is pressurized. As the coolant cools, it contracts and creates a vacuum in cooling system. This causes the vacuum valve to open and coolant in reserve/overflow tank to be drawn through connecting hose into radiator. If the vacuum valve is stuck shut, or overflow hose is kinked, radiator hoses will collapse on cool-down.

The radiator cooling fans are dual-speed electric motor driven fans. The radiator fan assembly includes two electric motors, two five blade fans, and a support shroud that is attached to the radiator. The radiator fans are serviced as an assembly.

OPERATION-GAS

Radiator fan operation is controlled by the Totally Integrated Power Module (TIPM), with inputs from the engine coolant temperature sensor, continuously variable transmission (CVT) oil temperature, and A/C head pressure. The (TIPM) turns on the fan through either the high or low speed fan relay. The PCM provides a ground to the relay's control circuit. The fan relays are located in the (TIPM). Refer to the label beneath the (TIPM) cover for location of fan relays.

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 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.

Scheme 14

Note. It is not necessary to discharge the air conditioning system to remove the radiator.

1. Disconnect negative battery cable.
2. Remove engine cover. Refer to «REMOVAL»(ref-304329-S27147758722008110700000) - 2.0L. Refer to «REMOVAL»(ref-304330-S22459581352008110700000) - 2.4L.
3. Remove air cleaner housing assembly. Refer to «REMOVAL»(ref-304329-S37258294512008110700000) - 2.0L. Refer to «REMOVAL»(ref-304330-S02290908592008110700000) - 2.4L.
4. Raise vehicle on hoist.
5. Drain cooling system. See «STANDARD PROCEDURE»(ref-304343-S02124729692008110700000) .
6. Disconnect radiator fan motor electrical connector.
7. Disconnect lower radiator hose.
8. Remove two lower fasteners attaching radiator fan shroud to radiator.
9. Disconnect Charger Air Cooler hoses from Charge Air Cooler.
10. Disconnect Charger Air Cooler from radiator.
11. Lower vehicle.
12. Remove grille.
13. Remove upper radiator hose from the radiator.
14. Remove remaining fasteners attaching radiator fan shroud to radiator.
15. Remove radiator fan/shroud assembly.
16. Remove remaining fasteners attaching AC condenser to radiator. Reposition AC condenser.
17. Unclip Charge Air Cooler from radiator remove radiator assembly by lifting it up from the engine compartment. Care should be taken not to damage the cooling fins and tubes during removal.

Scheme 15

1. Drain cooling system. See «STANDARD PROCEDURE»(ref-304343-S02124729692008110700000) .
2. Remove radiator fan. See «REMOVAL»(ref-304343-S09619904812008110700000) .
3. Disconnect lower radiator hose.
4. Remove fasteners attaching AC condenser to radiator. Reposition AC condenser.
5. Remove radiator assembly by lifting it up from the engine compartment. Care should be taken not to damage the cooling fins and tubes during removal.