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 ENGINE ELECTRICAL DIAGNOSTICS ).
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC's and to obtain cooling system data, (Refer to ENGINE ELECTRICAL DIAGNOSTICS ).
ERASING TROUBLE CODES
After the problem has been repaired, use the scan tool to erase a DTC. Refer to the ENGINE ELECTRICAL DIAGNOSTICS for operation of the scan tool.
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 DRAINING COOLING SYSTEM - ALL ENGINES . Remove accessory drive belt (Refer to BELTS-DRIVE .
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.
COOLING SYSTEM DIAGNOSIS CHART
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| TEMPERATURE GAUGE READS LOW | Has a Diagnostic Trouble Code (DTC) been set indicating a stuck open thermostat? Is the temperature sending unit connected? Is the temperature gauge operating OK? Coolant level low in cold ambient temperatures accompanied with poor heater performance. Improper operation of internal heater doors or heater controls. | (Refer to ENGINE ELECTRICAL DIAGNOSTICS ). Replace thermostat if necessary. Check the temperature sensor connector. Repair connector if necessary. Check gauge operation. (Refer to ENGINE TEMPERATURE INDICATOR ). Repair as necessary. Check coolant level in the coolant reserve/overflow tank or degas bottle and the radiator. Inspect system for leaks. Repair leaks as necessary. Refer to STANDARD PROCEDURE for WARNINGS and CAUTIONS associated with removing the radiator cap. Inspect heater and repair, as necessary, (Refer to HEATER PERFORMANCE ). |
| TEMPERATURE GAUGE READS HIGH OR THE COOLANT WARNING LAMP ILLUMINATES. COOLANT MAY OR MAY NOT BE LOST OR LEAKING FROM THE COOLING SYSTEM | Trailer is being towed, a steep hill is being climbed, vehicle is operated in slow moving traffic, or engine is being idled with very high ambient (outside) temperatures and the air conditioning is on. Higher altitudes could aggravate these conditions. Is the temperature gauge reading correctly? Is the temperature warning illuminating unnecessarily? Coolant low in coolant reserve/overflow tank and radiator? Pressure cap not installed tightly. If cap is loose, boiling point of coolant will be lowered. Also refer to the following Step 6. Poor seals at the radiator cap. Coolant level low in radiator but not in coolant reserve/overflow tank. This means the radiator is not drawing coolant from the coolant reserve/overflow tank as the engine cools Incorrect coolant concentration Coolant not flowing through system Radiator or A/C condenser fins are dirty or clogged. Radiator core is corroded or plugged. Dragging brakes Fuel or ignition system problems. Bug screen or cardboard is being, reducing airflow. Thermostat partially or completely shut. Viscous fan drive not operating properly. Cylinder head gasket leaking. Heater core leaking. | This may be a temporary condition and repair is not necessary. Turn off the air conditioning and attempt to drive the vehicle without any of the previous conditions. Observe the temperature gauge. The gauge should return to the normal range. If the gauge does not return to the normal range, determine the cause for overheating and repair. Refer to . Check gauge. (Refer to ). Repair as necessary. (Refer to ). Check for coolant leaks and repair as necessary. (Refer to DIAGNOSIS AND TESTING ). Tighten cap Check condition of cap and cap seals. Refer to . Replace cap if necessary. Check condition of radiator filler neck or degas bottle. If neck is bent or damaged, replace radiator or degas bottle. Check condition of radiator cap and cap seals. Refer to in this Group. Replace cap if necessary. Check condition of radiator filler neck. If neck is bent or damaged, replace radiator. Check condition of the hose from the radiator to the coolant tank. It should fit tight at both ends without any kinks or tears. Replace hose if necessary. Check coolant reserve/overflow tank and tanks hoses for blockage. Repair as necessary. Check coolant. (Refer to ) Check for coolant flow at radiator filler neck with some coolant removed, engine warm and thermostat open. Coolant should be observed flowing through radiator. If flow is not observed, determine area of obstruction and repair as necessary. Remove insects and debris. (Refer to - STANDARD PROCEDURE ). Have radiator re-cored or replaced. Check and correct as necessary. (Refer to - DIAGNOSIS AND TESTING ) Refer to or . Remove bug screen or cardboard. Check thermostat operation and replace as necessary. (Refer to - REMOVAL ). Check fan drive operation and replace as necessary. (Refer to - DIAGNOSIS AND TESTING ). Check for cylinder head gasket leaks. (Refer to - DIAGNOSIS AND TESTING ). Check heater core for leaks. (Refer to HEATER PERFORMANCE ). Repair as necessary. |
| TEMPERATURE GAUGE READING IS INCONSISTENT (FLUCTUATES, CYCLES, OR IS ERRATIC | During cold weather operation, with the heater in the high position, the gauge reading may drop slightly. Temperature gauge or engine mounted gauge sensor defective or shorted. Also, corroded or loose wiring in this circuit. Gauge reading rises when vehicle is brought to a stop after heavy use (engine still running) Gauge reading high after re-starting a warmed up (hot) engine. Coolant level low in radiator (air will build up in the cooling system causing the thermostat to open late). Cylinder head gasket leaking allowing exhaust gas to enter cooling system causing a thermostat to open late. Water pump impeller loose on shaft. Loose accessory drive belt, (water pump slipping) Air leak on the suction side of the water pump allows air to build up in cooling system causing thermostat to open late. | During cold weather operation, with the heater in the high position, the gauge reading may drop slightly. Check operation of gauge and repair if necessary. (Refer to ). A normal condition. No correction is necessary. Gauge should return to normal range after vehicle is driven. A normal condition. No correction is necessary. The gauge should return to normal range after a few minutes of engine operation. Check and correct coolant leaks. (Refer to - DIAGNOSIS AND TESTING ). Check for cylinder head gasket leaks. (Refer to - DIAGNOSIS AND TESTING ). (b) Check for coolant in the engine oil. Inspect for white steam emitting from the exhaust system. Repair as necessary. Check water pump and replace as necessary. (Refer to - REMOVAL ). Check and correct as necessary. (Refer to - DIAGNOSIS AND TESTING ) Locate leak and repair as necessary. |
| PRESSURE CAP IS BLOWING OFF STEAM AND/OR COOLANT TO COOLANT TANK. TEMPERATURE GAUGE READING MAY BE ABOVE NORMAL BUT NOT HIGH. COOLANT LEVEL MAY BE HIGH IN COOLANT RESERVE/OVERFLOW TANK | Pressure relief valve in radiator cap is defective. | Check condition of radiator cap and cap seals. (Refer to - DIAGNOSIS AND TESTING ). Replace cap as necessary. |
| COOLANT LOSS TO THE GROUND WITHOUT PRESSURE CAP BLOWOFF. GAUGE READING HIGH OR HOT | Coolant leaks in radiator, cooling system hoses, water pump or engine. | Pressure test and repair as necessary. (Refer to - DIAGNOSIS AND TESTING ). |
| DETONATION OR PRE-IGNITION (NOT CAUSED BY IGNITION SYSTEM). GAUGE MAY OR MAY NOT BE READING HIGH | Engine overheating. Freeze point of coolant not correct. Mixture is too rich or too lean. | Check reason for overheating and repair as necessary. Check coolant concentration. (Refer to ). |
| HOSE OR HOSES COLLAPSE WHILE ENGINE IS RUNNING | Vacuum created in cooling system on engine cool-down is not being relieved through coolant reserve/overflow system. | Radiator cap relief valve stuck. (Refer to - DIAGNOSIS AND TESTING ). Replace if necessary Hose between coolant reserve/overflow tank and radiator is kinked. Repair as necessary. Vent at coolant reserve/overflow tank is plugged. Clean vent and repair as necessary. Reserve/overflow tank is internally blocked or plugged. Check for blockage and repair as necessary. |
| NOISY VISCOUS FAN/DRIVE | Fan blades loose. Fan blades striking a surrounding object. Air obstructions at radiator or air conditioning condenser. Thermal viscous fan drive has defective bearing. A certain amount of fan noise may be evident on models equipped with a thermal viscous fan drive. Some of this noise is normal. | Replace fan blade assembly. (Refer to - REMOVAL ). Locate point of fan blade contact and repair as necessary. Remove obstructions and/or clean debris or insects from radiator or A/C condenser. Replace fan drive. Bearing is not serviceable. (Refer to - REMOVAL ). (Refer to - DESCRIPTION ) for an explanation of normal fan noise. |
| INADEQUATE HEATER PERFORMANCE. THERMOSTAT FAILED IN OPEN POSITION | Has a Diagnostic trouble Code (DTC) been set? Coolant level low Obstructions in heater hose/fittings Heater hose kinked Water pump is not pumping water to/through the heater core. When the engine is fully warmed up, both heater hoses should be hot to the touch. If only one of the hoses is hot, the water pump may not be operating correctly or the heater core may be plugged. Accessory drive belt may be slipping causing poor water pump operation. | (Refer to ENGINE ELECTRICAL DIAGNOSTICS ) for correct procedures and replace thermostat if necessary (Refer to STANDARD PROCEDURE ) Remove heater hoses at both ends and check for obstructions Locate kinked area and repair as necessary (Refer to - REMOVAL ) If a slipping belt is detected, (Refer to BELTS-DRIVE ). If heater core obstruction is detected, (Refer to HEATER PERFORMANCE ). |
| STEAM IS COMING FROM THE FRONT OF VEHICLE NEAR THE GRILL AREA WHEN WEATHER IS WET, ENGINE IS WARMED UP AND RUNNING, AND VEHICLE IS STATIONARY. TEMPERATURE GAUGE IS IN NORMAL RANGE | During wet weather, moisture (snow, ice or rain condensation) on the radiator will evaporate when the thermostat opens. This opening allows heated water into the radiator. When the moisture contacts the hot radiator, steam may be emitted. This usually occurs in cold weather with no fan or airflow to blow it away. | Occasional steam emitting from this area is normal. No repair is necessary. |
| COOLANT COLOR | Coolant color is not necessarily an indication of adequate corrosion or temperature protection, Do not rely on coolant color for determining condition of coolant. | (Refer to ) Adjust coolant mixture as necessary. |
| COOLANT LEVEL CHANGES IN COOLANT RESERVE/OVERFLOW TANK. TEMPERATURE GAUGE IS IN NORMAL RANGE | Level changes are to be expected as coolant volume fluctuates with engine temperature. If the level in the tank was between the FULL and ADD marks at normal operating temperature, the level should return to within that range after operation at elevated temperatures. | A normal condition. No repair is necessary. |
COOLING SYSTEM DIAGNOSIS CHART
VISUAL DIAGNOSIS
When diagnosing serpentine accessory drive belts, small cracks that run across the ribbed surface of the belt from rib to rib, are considered normal. These are not a reason to replace the 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 the belt if it has excessive wear, frayed cords or severe glazing.
Refer to ACCESSORY DRIVE BELT DIAGNOSIS CHART for further belt diagnosis.
Scheme 27
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.
Scheme 28
Scheme 29
Scheme 30
Scheme 31
| 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.
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. |
ON-BOARD DIAGNOSTICS
All gasoline powered models are equipped with On-Board Diagnostics for certain cooling system components. Refer to ENGINE ELECTRICAL DIAGNOSTICS 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 DIAGNOSIS AND TESTING for other probable causes. For other DTCs, (Refer to DIAGNOSIS AND TESTING )
The DTC can also be accessed through the DRB scan tool. Refer to DIAGNOSIS AND TESTING for diagnostic information and operation of the DRB scan tool.
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.
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.
| 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.