The powertrain control module (PCM) has been programmed to monitor certain cooling system components
- If the engine has remained cool for too long a period, such as with a stuck open thermostat, a Diagnostic Trouble Code (DTC) can be set.
- If an open or shorted condition has developed in the relay circuit controlling the electric radiator fan, a Diagnostic Trouble Code (DTC) can be set.
If the problem is sensed in a monitored circuit often enough to indicated an actual problem, a DTC is stored. The DTC will be stored in the PCM memory for eventual display to the service technician. (Refer to EMISSIONS CONTROL - DESCRIPTION) .
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC's and to obtain cooling system data, (Refer to EMISSIONS CONTROL - DESCRIPTION) .
ERASING TROUBLE CODES
After the problem has been repaired, use the scan tool to erase a DTC. Refer to the appropriate Engine ELECTRICAL DIAGNOSTICS service information for operation of the scan tool.
Scheme 10
A leak detection additive is available through the parts department that can be added to cooling system. The additive is highly visible under ultraviolet light (black light) (1). Pour one ounce of additive into cooling system. Place heater control unit in HEAT position. Start and operate engine until the radiator upper hose is warm to touch. Aim the commercially available black light tool at components to be checked. If leaks are present, black light will cause the additive to glow a bright green color.
The black light can be used in conjunction with a pressure tester to determine if any external leaks exist.
Scheme 11
The engine should be at normal operating temperature. Recheck the system cold if the cause of coolant loss is not located during the warm engine examination.
| WARNING | HOT, PRESSURIZED COOLANT CAN CAUSE INJURY BY SCALDING. |
Carefully remove the radiator pressure cap from the filler neck and check coolant level. Push down on cap to disengage it from the stop tabs. Wipe the inside of filler neck and examine the lower inside sealing seat for nicks, cracks, paint, dirt and solder residue. Inspect the radiator-to- reserve/overflow tank hose for internal obstructions. Insert a wire through the hose to be sure it is not obstructed.
Inspect cams on the outside of filler neck. If the cams are damaged, seating of the pressure cap valve and tester seal will be affected.
Attach pressure tester (7700 or an equivalent) to radiator filler neck (1).
Operate tester pump to apply 103.4 kPa (15 psi) pressure to system. If hoses enlarge excessively or bulge while testing, replace as necessary. Observe the gauge pointer and determine the condition of the cooling system according to the following criteria
Holds Steady: If the pointer remains steady for two minutes, serious coolant leaks are not present in system. However, there could be an internal leak that does not appear with normal system test pressure. If it is certain that coolant is being lost and leaks cannot be detected, inspect for interior leakage or perform Internal Leakage Test. Refer to INTERNAL LEAKAGE INSPECTION .
Drops Slowly: Indicates a small leak or seepage is occurring. Examine all connections for seepage or slight leakage with a flashlight. Inspect radiator, hoses, gasket edges and heater. Seal small leak holes with a Sealer Lubricant (or equivalent). Repair leak holes and inspect system again with pressure applied.
Drops Quickly: Indicates that serious leakage is occurring. Examine system for external leakage. If leaks are not visible, inspect for internal leakage. Large radiator leak holes should be repaired by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove engine oil pan drain plug and drain a small amount of engine oil. If coolant is present in the pan, it will drain first because it is heavier than oil. An alternative method is to operate engine for a short period to churn the oil. After this is done, remove engine dipstick and inspect for water globules. Also inspect the transmission dipstick for water globules and the transmission fluid cooler for leakage.
| WARNING | WITH RADIATOR PRESSURE TESTER TOOL INSTALLED ON RADIATOR, DO NOT ALLOW PRESSURE TO EXCEED 145 KPA (21 PSI). PRESSURE WILL BUILD UP QUICKLY IF A COMBUSTION LEAK IS PRESENT. TO RELEASE PRESSURE, ROCK TESTER FROM SIDE TO SIDE. WHEN REMOVING TESTER, DO NOT TURN TESTER MORE THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE. |
Operate the engine without the pressure cap on the radiator until the thermostat opens. Attach a Pressure Tester to filler neck. If pressure builds up quickly it indicates a combustion leak exists. This is usually the result of a cylinder head gasket leak or crack in engine. Repair as necessary.
If there is not an immediate pressure increase, pump the Pressure Tester. Do this until indicated pressure is within system range of 110 kPa (16 psi). Fluctuation of gauge pointer indicates compression or combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic converter, do not remove spark plug cables or short out cylinders to isolate compression leak.
If the needle on the dial of pressure tester does not fluctuate, race engine a few times to check for an abnormal amount of coolant or steam. This would be emitting from exhaust pipe. Coolant or steam from exhaust pipe may indicate a faulty cylinder head gasket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into cooling system is provided by a commercially available Block Leak Check tool. Follow manufacturers instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT PRESSURE TESTER
DO NOT WASTE reusable coolant. If the solution is clean, drain the coolant into a clean container for reuse.
| WARNING | DO NOT REMOVE CYLINDER BLOCK DRAIN PLUGS OR LOOSEN RADIATOR DRAINCOCK WITH SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR. |
Drain sufficient coolant to allow thermostat removal (Refer to COOLING - STANDARD PROCEDURE) . Remove accessory drive belt or (Refer to COOLING/ACCESSORY DRIVE/DRIVE BELTS - REMOVAL) .
Add coolant to radiator to bring level to within 6.3 mm (1/4 in) of the top of the thermostat housing.
| CAUTION | Avoid overheating. Do not operate engine for an excessive period of time. Open draincock immediately after test to eliminate boil over. |
Start engine and accelerate rapidly three times, to approximately 3000 RPM while observing coolant. If internal engine combustion gases are leaking into cooling system, bubbles will appear in coolant. If bubbles do not appear, internal combustion gas leakage is not present.
NOISE DIAGNOSIS
Noises generated by the accessory drive belt are most noticeable at idle. Before replacing a belt to resolve a noise condition, inspect all of the accessory drive pulleys for alignment, glazing, or excessive end play.
| 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 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. Inspect belt. | |
| 5. Belt rubber deteriorated | 5. Replace belt | |
| BELT SLIPS | 1. Belt slipping because of insufficient tension | 1. Inspect/Replace tensioner if necessary |
| 2. Belt or pulley exposed to substance that has reduced friction (belt dressing, oil, ethylene glycol) | 2. Replace belt and clean pulleys | |
| 3. Driven component bearing failure (seizure) | 3. Replace faulty component or bearing | |
| 4. Belt glazed or hardened from heat and excessive slippage | 4. Replace belt. | |
| LONGITUDAL BELT CRACKING | 1. Belt has mistracked from pulley groove | 1. Replace belt |
| 2. Pulley groove tip has worn away rubber to tensile member | 2. Replace belt | |
| "GROOVE JUMPING" (Belt does not maintain correct position on pulley) | 1. Incorrect belt tension | 1. Inspect/Replace tensioner if necessary |
| 2. Pulley(s) not within design tolerance | 2. Replace pulley(s) | |
| 3. Foreign object(s) in grooves | 3. Remove foreign objects from grooves | |
| 4. Pulley misalignment | 4. Align component | |
| 5. Belt cordline is broken | 5. Replace belt | |
| BELT BROKEN (Note: Identify and correct problem before new belt is installed) | 1. Incorrect belt tension | 1. Replace Inspect/Replace tensioner if necessary |
| 2. Tensile member damaged during belt installation | 2. Replace belt | |
| 3. Severe misalignment | 3. Align pulley(s) | |
| 4. Bracket, pulley, or bearing failure | 4. Replace defective component and belt | |
| NOISE (Objectionable squeal, squeak, or rumble is heard or felt while drive belt is in operation) | 1. Incorrect belt tension | 1. Inspect/Replace tensioner if necessary |
| 2. Bearing noise | 2. Locate and repair | |
| 3. Belt misalignment | 3. Align belt/pulley(s) | |
| 4. Belt to pulley mismatch | 4. Install correct belt | |
| 5. Driven component induced vibration | 5. Locate defective driven component and repair | |
| TENSION SHEETING FABRIC FAILURE (Woven fabric on outside, circumference of belt has cracked or separated from body of belt) | 1. Tension sheeting contacting stationary object | 1. Correct rubbing condition |
| 2. Excessive heat causing woven fabric to age | 2. Replace belt | |
| 3. Tension sheeting splice has fractured | 3. Replace belt | |
| CORD EDGE FAILURE (Tensile member exposed at edges of belt or separated from belt body) | 1. Incorrect belt tension | 1. Inspect/Replace tensioner if necessary |
| 2. Belt contacting stationary object | 2. Replace belt | |
| 3. Pulley(s) out of tolerance | 3. Replace pulley | |
| 4. Insufficient adhesion between tensile member and rubber matrix | 4. Replace belt |
ACCESSORY DRIVE BELT DIAGNOSIS CHART
Scheme 12
| CAUTION | DO NOT LET TENSIONER ARM SNAP BACK TO THE FREEARM POSITION, SEVER DAMAGE MAY OCCUR TO THE TENSIONER. |
Belt tension is not adjustable. Belt adjustment is maintained by an automatic (spring load) belt tensioner.
- Disconnect negative battery cable from battery.
- Rotate belt tensioner (6) until it contacts it's stop. Remove belt (2), then slowly rotate the tensioner (6) into the freearm position.
Scheme 13
Belt tension is not adjustable. Belt adjustment is maintained by an automatic (spring load) belt tensioner.
Scheme 14
- Check condition of all pulleys. CAUTION: When installing the serpentine accessory drive belt, the belt MUST be routed correctly. If not, the engine may overheat due to the water pump rotating in the wrong direction.
- Install new belt. Route the belt around all pulleys except the idler pulley (5). Rotate the tensioner arm until it contacts it's stop position. Route the belt around the idler (5) and slowly let the tensioner rotate into the belt. Make sure the belt is seated onto all pulleys.
- With the drive belt installed, inspect the belt wear indicator. On 4.7L Engines only, the gap between the tang and the housing stop (measurement A) must not exceed 24 mm (.94 inches). If the measurement exceeds this specification replace the serpentine accessory drive belt.
DIAGNOSIS AND TESTING - ENGINE BLOCK HEATER
If the unit does not operate, possible causes can be either the power cord or the heater element. Test the power cord for continuity with a 110-volt voltmeter or 110-volt test light. Test heater element continuity with an ohmmeter or a 12-volt test light.
| CAUTION | To prevent damage, the power cord must be secured in it's retainer clips and away from any components that may cause abrasion or damage, such as linkages, exhaust components, etc. |
Scheme 15
Scheme 16
- Disconnect negative battery cable from battery.
- Drain coolant from radiator «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .
- Raise vehicle.
- Remove engine cylinder block drain plug(s) (1) located on the sides of cylinder block above the oil pan rail.
- Remove power cord from block heater.
- Loosen screw at center of block heater. Remove heater assembly (1).
ON-BOARD DIAGNOSTICS
All gasoline powered models are equipped with On-Board Diagnostics for certain cooling system components. Refer to On-Board Diagnostics (OBD) in the EMISSIONS article of this information for additional information. If the powertrain control module (PCM) detects low engine coolant temperature, it will record a Diagnostic Trouble Code (DTC) in the PCM memory. Do not change a thermostat for lack of heat as indicated by the instrument panel gauge or by poor heater performance unless a DTC is present. Refer to the appropriate Engine ELECTRICAL DIAGNOSTIC article of this information for other probable causes. For other DTCs, (Refer to EMISSIONS CONTROL - DESCRIPTION)
The DTC can also be accessed through the DRB scan tool. Refer to the appropriate Engine ELECTRICAL DIAGNOSTIC for information on operation of the DRB scan tool.
Scheme 17
If thermostat is being replaced, be sure that replacement is specified thermostat for vehicle model and engine type.
- Disconnect negative battery cable at battery.
- Drain cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000)
- Raise vehicle on hoist.
- Remove splash shield.
- Remove lower radiator hose clamp and lower radiator hose at thermostat housing.
- Remove thermostat housing mounting bolts , thermostat housing (1) and thermostat (3).
INSPECTION
The radiator cooling fins should be checked for damage or deterioration. Inspect cooling fins to make sure they are not bent or crushed, these areas result in reduced heat exchange causing the cooling system to operate at higher temperatures. Inspect the plastic end tanks for cracks, damage or leaks.
Inspect the radiator neck for damage or distortion.
Hold cap at eye level, right side up. The vent valve at bottom of cap should open. If rubber gasket has swollen and prevents vent valve from opening, replace cap.
Hold cap at eye level, upside down. If any light can be seen between vent valve and rubber gasket, replace cap. Do not use a replacement cap that has a spring to hold vent shut. A replacement cap must be the type designed for a coolant reserve/overflow system with a completely sealed diaphragm spring and a rubber gasket. This gasket is used to seal to radiator filler neck top surface. Use of proper cap will allow coolant return to radiator.
Scheme 18
A centrifugal water pump (1) circulates coolant through the water jackets, passages, intake manifold, radiator core, cooling system hoses and heater core. The pump is driven from the engine crankshaft by a single serpentine drive belt that drives the water pump pulley (1).
The water pump impeller is pressed onto the rear of a shaft that rotates in bearings pressed into the housing. The housing has two small holes to allow seepage to escape. The water pump seals are lubricated by the antifreeze in the coolant mixture. No additional lubrication is necessary.
Both heater hoses are connected to fittings on the timing chain front cover. The water pump is also mounted directly to the timing chain cover and is equipped with a non serviceable integral pulley.
Scheme 19
The 4.7L engine uses an internal water/coolant bypass system. The design uses galleries in the timing chain cover to circulate coolant during engine warm-up preventing the coolant from flowing through the radiator.
Inspect the water pump assembly for cracks in the housing, water leaks from shaft seal, worn bearing or impeller rubbing either the pump body or timing chain case/cover.
Scheme 20
- Clean gasket mating surfaces.
- Using a new gasket, position water pump (1) and install mounting bolts as shown. Tighten the water pump mounting bolts to 24 N.m (18 ft. lbs.) for 3.7L engines. On 4.7L engines, for appropriate bolt tightening specification, refer to «FASTENER IDENTIFICATION»(ref-285315-S01285940972008052100000) .
- Spin water pump to be sure that pump impeller does not rub against timing chain case/cover.
- Connect radiator upper hose to water pump.
- Install accessory drive belt «(Refer to COOLING/ACCESSORY DRIVE/DRIVE BELTS - INSTALLATION)»(ref-247624-S16163766032007020100000) .
- Position fan shroud and fan blade/viscous fan drive assembly.
- Install two fan shroud-to-radiator screws.
- Be sure of at least 25 mm (1.0 inches) between tips of fan blades and fan shroud.
- Install fan blade/viscous fan drive assembly to water pump shaft «INSTALLATION»(ref-247624-S41387860932007022000000) .
- Fill cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .
- Connect negative battery cable.
- Start and warm the engine. Check for leaks.
Scheme 21
The thermal viscous fan drive (3) is a silicone fluid filled coupling used to connect the fan blades to the water pump shaft (4). The coupling allows the fan to be driven in a normal manner. This is done at low engine speeds while limiting the top speed of the fan to a predetermined maximum level at higher engine speeds.
Scheme 22
A thermostatic bimetallic spring coil (2) is located on the front face of the viscous fan drive unit (1). 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.
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.
| WARNING | DO NOT ATTEMPT TO BEND OR STRAIGHTEN FAN BLADES IF FAN IS NOT WITHIN SPECIFICATIONS. |
| CAUTION | If fan blade assembly is replaced because of mechanical damage, water pump and viscous fan drive should also be inspected. These components could have been damaged due to excessive vibration. |
- Remove fan blade assembly from viscous fan drive unit (four bolts).
- Lay fan on a flat surface with leading edge facing down. With tip of blade touching flat surface, replace fan if clearance between opposite blade and surface is greater than 2.0 mm (.090 inch). Rocking motion of opposite blades should not exceed 2.0 mm (.090 inch). Test all blades in this manner.
- Inspect fan assembly for cracks, bends, loose rivets or broken welds. Replace fan if any damage is found.