DESCRIPTION
The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible, maintains normal operating temperature and prevents overheating.
The cooling system also provides a means of heating the passenger compartment. The cooling system is pressurized and uses a centrifugal water pump to circulate coolant throughout the system. A separate and remotely mounted, pressurized coolant tank using a pressure/vent cap is used.
The accessory drive belt is a serpentine type belt. Satisfactory performance of these belts depends on belt condition and proper belt tension.
Scheme 6
| 1 - NORMAL CRACKS BELT OK |
|---|
| 2 - NOT NORMAL CRACKS REPLACE BELT |
When diagnosing serpentine drive belts, small cracks (1) that run across ribbed surface of belt from rib to rib, are considered normal. These are not a reason to replace belt. However, cracks running along a rib (not across) are not normal. Any belt with cracks running along a rib must be replaced. Also replace belt if it has excessive wear, frayed cords or severe glazing.
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| RIB CHUNKING (ONE OR MORE RIBS HAS SEPARATED FROM BELT BODY) | 1. Foreign objects imbedded in pulley grooves. | 1. Remove foreign objects from pulley grooves. Replace belt. |
| 2. Installation damage. | 2. Replace belt. | |
| RIB OR BELT WEAR | 1. Pulley(s) misaligned. | 1. Align pulley(s). |
| 2. Abrasive environment. | 2. Clean pulley(s). Replace belt if necessary. | |
| 3. Rusted pulley(s). | 3. Clean rust from pulley(s). | |
| 4. Sharp or jagged pulley groove tips. | 4. Replace pulley. | |
| 5. Rubber deteriorated. | 5. Replace belt. | |
| LONGITUDINAL BELT CRACKING (CRACKS BETWEEN TWO RIBS) | 1. Belt has mistracked from pulley groove. | 1. Replace belt. |
| 2. Pulley groove tip has worn away rubber to tensile member. | 2. Replace belt. | |
| BELT SLIPS | 1. Belt slipping because of insufficient tension. | 1. Replace automatic belt tensioner. |
| 2. Belt routed incorrectly. | 2. Verify belt routing. | |
| 3. Incorrect belt. | 3. Replace belt. | |
| 4. Belt or pulley subjected to substance (belt dressing, oil ethylene glycol) that has reduced friction. | 4. Replace belt and clean pulleys. | |
| 5. Driven component bearing failure. | 5. Replace faulty component bearing. | |
| 6. Belt glazed and hardened from heat and excessive slippage. | 6. Replace belt. | |
| "GROOVE JUMPING" (BELT DOES NOT MAINTAIN CORRECT POSITION ON PULLEY) | 1. Belt tension either too high or too low. | 1. Replace automatic belt tensioner. |
| 2. Belt routed incorrectly. | 2. Verify belt routing. | |
| 3. Incorrect belt. | 3. Replace belt. | |
| 4. Pulley(s) not within design tolerance. | 4. Replace pulley(s). | |
| 5. Foreign object(s) in grooves. | 5. Remove foreign objects from grooves. | |
| 6. Pulley misalignment. | 6. Check and replace. | |
| 7. Belt cord line is broken. | 7. Replace belt. | |
| BELT BROKEN (NOTE: IDENTIFY AND CORRECT PROBLEM BEFORE NEW BELT IS INSTALLED) | 1. Excessive tension. | 1. Replace belt and automatic belt tensioner. |
| 2. Incorrect belt. | 2. Replace belt. | |
| 3. Tensile member damaged during belt installation. | 3. Replace belt. | |
| 4. Severe misalignment. | 4. Check and replace. | |
| 5. Bracket, pulley, or bearing failure. | 5. Replace defective component and belt. | |
| NOISE (OBJECTIONABLE SQUEAL, SQUEAK, OR RUMBLE IS HEARD OR FELT WHILE DRIVE BELT IS IN OPERATION) | 1. Belt slippage. | 1. Replace belt or automatic belt tensioner. |
| 2. Bearing noise. | 2. Locate and repair. | |
| 3. Belt misalignment. | 3. Replace belt. | |
| 4. Belt-to-pulley mismatch. | 4. Install correct belt. |
SERPENTINE DRIVE BELT DIAGNOSIS CHART
Scheme 7
| 1 - WITH A/C |
|---|
| 2 - WITHOUT A/C |
| CAUTION | Do not let tensioner arm snap back to the freearm position, severe damage may occur to the tensioner. |
Scheme 8
Scheme 9
Scheme 10
- Disconnect negative battery cable.
- Rotate the belt tensioner (1) until the position locking tabs (3 and 4) line up.
- Install a drift into the belt tensioner (1) at position 2.
- Remove the accessory drive belt (1).
Scheme 11
| 1 - GENERATOR PULLEY |
|---|
| 2 - ACCESSORY DRIVE BELT |
| 3 - POWER STEERING PUMP PULLEY |
| 4 - CRANKSHAFT PULLEY |
| 5 - IDLER PULLEY |
| 6 - TENSIONER |
| 7 - A/C COMPRESSOR PULLEY |
| 8 - WATER PUMP PULLEY |
| CAUTION | Do not let tensioner arm snap back to the freearm position, severe damage may occur to the tensioner. |
- Disconnect negative battery cable.
- Remove combination washer reservoir/coolant recovery container. See «REMOVAL»(ref-306154-S39360093762008120900000) .
- Rotate belt tensioner (6) until it contacts its stop. Remove belt, then slowly rotate the tensioner into the freearm position.
Scheme 12
| 1 - GENERATOR |
|---|
| 2 - IDLER PULLEY |
| 3 - WATER PUMP PULLEY |
| 4 - CRANKSHAFT PULLEY |
| 5 - ACCESSORY DRIVE BELT TENSIONER |
| 6 - A/C COMPRESSOR |
| 7 - ACCESSORY DRIVE BELT |
- Remove combination coolant recovery/washer reservoir. See «REMOVAL»(ref-306154-S39360093762008120900000) .
- Insert a suitable square drive ratchet into the square hole on belt tensioner arm.
- Rotate accessory drive belt tensioner clockwise to release belt tension.
- Remove accessory drive belt.
The automatic belt tensioner is a spring loaded arm and pulley assembly. The tensioner assembly is designed to apply constant pressure on the accessory drive belt to maintain proper belt tension.
OPERATION
| WARNING | The automatic belt tensioner assembly is spring loaded. Do not attempt to disassemble the tensioner assembly. |
The automatic belt tensioner maintains correct belt tension using a coiled spring within the tensioner housing. The spring applies pressure to the tensioner arm pressing the arm into the belt, tensioning the belt.
If a new belt is being installed, the arrow must be within approximately 3 mm (1/8 in.) of indexing mark. Belt is considered new if it has been used 15 minutes or less. If this specification cannot be met, check for
- The wrong belt being installed (incorrect length/width)
- Worn bearings on an engine accessory (A/C compressor, power steering pump, water pump, idler pulley or generator)
- A pulley on an engine accessory being loose
- Misalignment of an engine accessory
- Belt incorrectly routed.
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.
The block heater is operated by ordinary house current (110 Volt AC) through a power cord and connector located in the engine compartment. 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.
| 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 block heater element is submerged in the cooling system's coolant. When electrical power (110 volt AC) 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.
Scheme 13
| 1 - POWER CORD |
|---|
| 2 - BLOCK HEATER |
| 3 - CORE HOLE |
- Drain cooling system. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
- Raise vehicle on hoist.
- Detach power cord plug from heater.
- Loosen screw in center of heater. Remove heater assembly.
The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.
At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return).
When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the following calculations
- for engine coolant temperature gauge operation through the bus communications
- Injector pulse-width
- Spark-advance curves
- ASD relay shut-down times
- Idle Air Control (IAC) motor key-on steps
- Pulse-width prime-shot during cranking
- O2 sensor closed loop times
- Purge solenoid on/off times
- EGR solenoid on/off times (if equipped)
- Leak Detection Pump operation (if equipped)
- Radiator fan relay on/off times (if equipped)
- Target idle speed
Scheme 14
| 1 - CYLINDER HEAD BOLT |
|---|
| 2 - GLOW PLUG |
| 3 - COOLANT FITTING |
| 4 - CYLINDER HEAD ALIGNMENT DOWEL |
| 5 - GLOW PLUG HARNESS |
| 6 - CYLINDER LINER |
| 7 - CYLINDER BLOCK |
| 8 - CYLINDER HEAD GASKET |
| 9 - CYLINDER HEAD |
| 10 - ROCKER ARM ASSEMBLIES |
| WARNING | Do not remove or loosen the coolant pressure/vent cap, cylinder block drain plugs, or the draincock when the system is hot and under pressure because serious burns from the coolant can occur. |
- Disconnect negative battery cable.
- Drain the cooling system. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
- Disconnect coolant temperature sensor electrical connector.
- Remove coolant temperature sensor (3) from cylinder head.
Scheme 15
| 1 - MOUNTING SCREWS |
|---|
| 2 - MAP SENSOR |
| 3 - ECT SENSOR |
| 4 - FRONT OF INTAKE MANIFOLD |
The Engine Coolant Temperature (ECT) sensor (3) is installed into a water jacket at front of intake manifold near rear of generator.
| WARNING | Hot, pressurized coolant can cause injury by scalding. Cooling system must be partially drained before removing the coolant temperature sensor. |
- Partially drain cooling system.
- Disconnect electrical connector from sensor.
- Remove sensor from intake manifold.
The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relays. The PCM regulates fan operation based on input from the engine coolant temperature sensor, battery temperature sensor, air conditioning select switch and vehicle speed.
The fan is not energized during engine cranking regardless of the electrical input from the temperature sensors and air conditioning switch. However, if engine operation conditions warrant fan engagement, the fan will run once engine starts.
On vehicles NOT equipped with AC: The relay is energized when the coolant temperature is above 80°C (176°F), or battery temperature sensor above -12°C (10°F). It will then de-energize when coolant temperature drops below 82°C (180°F), or battery temperature sensor below -9°C (16°F).
Vehicles Equipped with AC: In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the, air conditioning system is activated. The relay is also energized when air conditioning is selected and coolant temperature is above 95°C (203°F), or, air conditioning is selected and battery temperature sensor is above 41°C (106°F). It will then de-energize when air conditioning is selected and coolant temperature is below 92°C (198°F), or air conditioning is selected and battery temperature is below 38°C (100°F).
Scheme 16
| 1 - SPECIAL TOOL 6958 SPANNER WRENCH WITH ADAPTER PINS 8346 |
|---|
| 2 - FAN |
If the fan blade is bent, warped, cracked or damaged in any way, it must be replaced only with a replacement fan blade. Do not attempt to repair a damaged fan blade.
Note. For 3.7L Heavy Duty/Max Cool/Trailer Tow cooling package, the viscous fan cannot be removed separate from the shroud. Both fan and shroud must be removed together.
- Disconnect battery negative cable.
- Using special tool 6958 spanner wrench and 8346 adapters, remove the viscous fan from the water pump. (Scheme 16) 1 - RADIATOR 2 - ELECTRIC COOLING FAN CONNECTOR 3 - FAN SHROUD 4 - 2 SPEED ELECTRIC COOLING FAN
- Gently lay fan into shroud.
- Disconnect the electrical connector (2) for the electric fan, then disconnect connector from shroud.
- Remove the two fan shroud mounting bolts connecting the fan shroud to the radiator. see scheme 53
- Remove the shroud and fan from the vehicle.
A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced RPM regardless of engine speed. Normally less than 800 RPM.
Only when sufficient heat is present, will the viscous fan drive engage. This is when the air flowing through the radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and the fan speed is reduced to the previous disengaged speed.
The thermostat starts to open at 80°C (176°F). Above this temperature, coolant is allowed to flow to the radiator. This provides quicker engine warm-up and overall temperature control.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation. This condensation can result in sludge formation.
The pressure cap allows the cooling system to operate at higher than atmospheric pressure which raises the coolant boiling point, thus allowing increased radiator cooling capacity. The pressure cap releases pressure at some point within a range of 110 kPa ± 14 kPa (16 psi ± 2 psi).
A spring-loaded vent valve in the center of the cap 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.
| CAUTION | Use only the pressure cap specified for this vehicle. Use of other pressure caps can lead to coolant loss and overheating. |
Scheme 17
| 1 - OVERFLOW NIPPLE |
|---|
| 2 - MAIN SPRING |
| 3 - GASKET RETAINER |
| 4 - STAINLESS-STEEL SWIVEL TOP |
| 5 - RUBBER SEALS |
| 6 - VENT VALVE |
| 7 - PRESSURE BOTTLE |
| 8 - FILLER NECK |
The pressure cap upper gasket (seal) pressure relief can be checked by removing the overflow hose at the radiator filler neck nipple. Attach the Pressure Tester 7700 to the filler neck nipple (1) and pump air into the radiator. Pressure cap upper gasket should relieve at 69-124 kPa (10-18 psi) and hold pressure at 55 kPa (8 psi) minimum.
| WARNING | The warning words "do not open hot" on the radiator pressure cap is a safety precaution. When hot, pressure builds up in cooling system. To prevent scalding or injury, the radiator cap should not be removed while the system is hot or under pressure. |
There is no need to remove the radiator cap at any time except for the following purposes
- Check and adjust coolant freeze point.
- Refill system with new coolant.
- Conducting service procedures.
- Checking for vacuum leaks.
| WARNING | If vehicle has been run recently, wait 15 minutes before removing cap. Then place a shop towel over the cap and without pushing down rotate counterclockwise to the first stop. Allow fluids to escape through the overflow tube and when the system stops pushing coolant and steam into the CRS tank and pressure drops push down and remove the cap completely. Squeezing the radiator inlet hose with a shop towel (to check pressure) before and after turning to the first stop is recommended. |
Scheme 18
| 1 - PRESSURE CAP |
|---|
| 2 - PRESSURE TESTER |
Dip the pressure cap (1) in water. Clean any deposits off the vent valve or its seat and apply cap to end of the Pressure Cap Test Adapter that is included with the Pressure Tester 7700. Working the plunger, bring the pressure to 104 kPa (15 psi) on the gauge. If the pressure cap fails to hold pressure of at least 97 kPa (14 psi), replace the pressure cap.
| CAUTION | The Cooling System Tester Tool is very sensitive to small air leaks that will not cause cooling system problems. A pressure cap that does not have a history of coolant loss should not be replaced just because it leaks slowly when tested with this tool. Add water to the tool. Turn tool upside down and recheck pressure cap to confirm that cap is bad. |
If the pressure cap tests properly while positioned on Pressure Tester (2), but will not hold pressure or vacuum when positioned on the filler neck. Inspect the filler neck and cap top gasket for irregularities that may prevent the cap from sealing properly.
The automatic transmission cooler is located in the front of the condenser and behind the front fascia. The transmission cooler is a heat exchanger that allows heat in the transmission fluid to be transferred to the air passing over the cooler fins.
The transmission oil cooler for the 2.8L Diesel with automatic transmission integrated into the A/C condenser.
The Transmission oil cooler assembly is equipped with quick connect fitting for the transmission oil cooler lines.