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Diagnosis And Testing - Cooling System Diagnosis

COOLING SYSTEM DIAGNOSIS

CONDITION POSSIBLE CAUSE CORRECTION
TEMPERATURE GAUGE READS LOW
  1. Diagnostic Trouble Code (DTC) set indicating a stuck open engine thermostat.
  2. Problem with engine coolant temperature (ECT) sensor or circuit.
  3. Problem with Temperature gauge.
  4. Coolant level low during cold ambient temperature, accompanied by poor heater performance.
  1. Refer to Appropriate Diagnostic Information. Replace thermostat, if necessary. If a (DTC) has not been set, the problem may be with the temperature gauge.
  2. Refer to the Appropriate Diagnostic Information for checking the ECT sensor
  3. Check Gauge operation. (Refer to the Appropriate Diagnostic Information)
  4. Check coolant level. (refer to STANDARD PROCEDURE ) Inspect the system for leaks. Repair as necessary.
TEMPERATURE GAUGE READS HIGH OR ENGINE COOLANT WARNING LAMP ILLUMINATES. COOLANT MAY OR MAY NOT BE LOST FROM SYSTEM.
  1. Trailer being towed, a steep hill being climbed, vehicle being operated in slow moving traffic, or engine idling during high ambient (outside) temperatures with air conditioning on. High altitudes could cause these conditions.
  2. Is temperature gauge (if equipped) reading correctly?
  3. Is temperature warning lamp (if equipped) illuminating unnecessarily?
  4. Low coolant level.
  5. Pressure cap not installed tightly. If cap is loose, boiling point of coolant will be lowered. Also refer to the following step 6.
  6. Poor seals at pressure cap.
  7. Wrong pressure cap installed.
  8. 2.4L Vehicles: Coolant level low in radiator, but not in coolant recovery container. This indicates the radiator is not drawing coolant from the coolant recovery container as the engine cools. As the engine cools, a vacuum is formed inside the cooling system. If the radiator cap seals are defective, or the cooling system has a leak, a vacuum cannot be formed.
  9. Freeze point of coolant not correct. Mixture ratio may be too rich.
  10. Coolant not flowing through system.
  11. Radiator or A/C condenser fins are dirty or clogged.
  12. Radiator core is plugged or corroded.
  13. Fuel or ignition system problems.
  14. Dragging Brakes.
  15. Bug screen or other aftermarket accessory is being used causing reduced air flow.
  16. Thermostat partially or completely closed.
  17. Electric radiator fan not operating properly.
  18. Cylinder head gasket leaking.
  19. Heater core leaking.
  1. This may be a temporary condition and repair is not necessary. Turn off the air conditioning and 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 of the overheating and repair. Refer to POSSIBLE CAUSES.
  2. Check the gauge. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  3. Check warning lamp operation. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  4. Check for coolant leaks. (Refer to DIAGNOSIS AND TESTING - COOLING SYSTEM LEAK TESTING ) Repair as necessary.
  5. Tighten pressure cap.
  6. Check the following:
    1. Check condition of cap and cap seals. (Refer to INSPECTION ) Replace cap if necessary.
    2. Check condition of filler neck. If neck is damaged, replace as necessary.
  7. Vehicles equipped with 2.4L engines use different pressure caps than vehicles equipped with 2.7L engines. Verify proper pressure cap part number.
    1. Check condition of pressure cap and seals. Replace cap if necessary.
    2. Check condition of filler neck. Replace if damaged.
    3. Check condition of hose from filler neck to coolant container. It should be tight at both ends without any kinks or tears. Replace hose as necessary.
    4. Check coolant recovery container and hose for blockage. Repair as necessary.
  9. Check coolant concentration. (Refer to DIAGNOSIS AND TESTING - COOLANT CONCENTRATION TESTING ) Adjust glycol-to-water ratio as required.
  10. Check the following:
    1. 2.4L Vehicles: Check for coolant flow at filler neck with some coolant removed, engine warm, and thermostat open. Coolant should be observed flowing through filler neck. If flow is not observed, determine reason for lack of flow and repair as necessary.
    2. 2.7L Vehicles: Engine coolant motion should be observable in coolant pressure container when revving the engine while running.
  11. Clean obstruction from fins.
  12. Clean or replace radiator as necessary.
  13. (Refer to the Appropriate Diagnostic Information)
  14. Inspect brake system and repair as necessary. (Refer to appropriate BRAKES article.)
  15. Remove bug screen or accessory.
  16. Check thermostat operation and replace as necessary. (Refer to DIAGNOSIS AND TESTING - ENGINE COOLANT THERMOSTAT TESTING )
  17. Check electric fan operation and repair as necessary.
  18. Check cylinder head gasket for leaks. (Refer to appropriate ENGINES article).
  19. Check heater core for leaks. Repair as necessary.
TEMPERATURE GAUGE READING IS INCONSISTENT (FLUCTUATES, CYCLES OR IS ERRATIC)
  1. The gauge may cycle up and down. This is due to the cycling of the electric radiator fan and/or changing vehicle operating conditions.
  2. During cold weather operation with the heater blower in the high position, the gauge reading may drop slightly.
  3. Temperature gauge or engine coolant temperature sensor is defective or shorted.
  4. Gauge reading rises when vehicle is brought to a stop after heavy use (engine still running).
  5. Gauge reading high after restarting a warmed-up (hot) engine.
  6. Coolant level low (air will build up in the cooling system causing the thermostat to open late).
  7. Cylinder head gasket leaking allowing exhaust gas to enter cooling system. This will cause thermostat to open late.
  8. Water pump impeller or pulley loose on shaft.
  9. Air leak on the suction side of water pump allows air to build up in cooling system. This will cause the thermostat to open late.
  1. A normal condition. No correction is necessary. If gauge cycling is going into the hot zone, check electric fan operation and repair as necessary. (Refer to DIAGNOSIS AND TESTING )
  2. A normal condition. No correction is necessary.
  3. Check operation of gauge and repair as necessary. (Refer to the Appropriate Diagnostic Information)
  4. A normal condition. No correction is necessary. The gauge should return to normal range after vehicle is driven.
  5. A normal condition. No correction is necessary. The gauge should return to normal range after a few minutes of engine operation.
  6. Check cooling system for leaks. Repair as necessary. (Refer to DIAGNOSIS AND TESTING )
  7. Check the following:
    1. Check for cylinder head gasket leaks. Repair as necessary. (Refer to appropriate ENGINES article)
    2. Check for coolant in the engine oil. Inspect for white steam emitting from exhaust system. Repair as necessary.
  8. Check water pump and replace as necessary.
  9. Locate leak and repair as necessary.
PRESSURE CAP IS BLOWING OFF STEAM AND/OR COOLANT FLOWING INTO RECOVERY CONTAINER. TEMPERATURE GAUGE READING MAY BE ABOVE NORMAL, BUT NOT HIGH. COOLANT LEVEL MAY BE HIGH IN RECOVERY CONTAINER.
  1. Pressure relief valve in pressure cap defective or wrong pressure cap installed.
  1. Verify proper pressure cap part number. Check condition of pressure cap and seals. Replace as necessary. (Refer to DIAGNOSIS AND TESTING )
COOLANT LOSS TO THE GROUND WITHOUT PRESSURE CAP BLOWOFF. GAUGE IS READING HIGH OR HOT.
  1. Coolant leaks in radiator, cooling system hoses, water pump or engine.
  1. Pressure test and repair as necessary. (Refer to DIAGNOSIS AND TESTING - COOLING SYSTEM LEAK TESTING )
DETONATION OR PRE-IGNITION (NOT CAUSED BY IGNITION SYSTEM). GAUGE MAY OR MAY NOT BE READING HIGH.
  1. Engine overheating.
  2. Freeze point of coolant not correct.
  1. Check reason for overheating and repair as necessary.
  2. Check the freeze point of the coolant. (Refer to DIAGNOSIS AND TESTING - COOLANT CONCENTRATION TESTING ) Adjust glycol-to-water ratio as required.
HOSE OR HOSES COLLAPSE WHEN ENGINE IS COOLING
  1. Vacuum created in cooling system on engine cool-down is not being relieved through coolant recovery container system.
    1. Radiator pressure cap relief valve stuck. (Refer to DIAGNOSIS AND TESTING ) Replace as necessary.
    2. Hose between coolant recovery container and radiator is kinked. Repair as necessary.
    3. Vent at coolant recovery container is plugged. Clean vent and repair as necessary.
    4. Coolant recovery container is internally blocked or plugged. Check for blockage and repair as necessary.
ELECTRIC RADIATOR FAN OPERATES ALL THE TIME.
  1. Fan relay, powertrain control module (PCM) or engine coolant temperature sensor defective.
  2. Check for low coolant level.
  1. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  2. (Refer to STANDARD PROCEDURE ) Repair as necessary.
ELECTRIC RADIATOR FAN WILL NOT OPERATE. GAUGE READING HIGH OR HOT
  1. Radiator fan motor defective.
  2. Radiator fan relay, powertrain control module (PCM) or engine coolant temperature sensor defective.
  3. Blown fuse in power distribution center (PDC).
  1. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  2. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  3. Determine reason for blown fuse and repair as necessary.
NOISY FAN
  1. Radiator fan blade loose.
  2. Radiator fan blade striking a surrounding object.
  3. Air obstructions at radiator or A/C condenser.
  4. Radiator fan motor defective.
  1. Replace fan assembly.
  2. Locate point of fan blade contact and repair as necessary.
  3. Remove obstructions and/or clean debris from radiator and/or A/C condenser.
  4. Replace as necessary. (Refer to REMOVAL )
INADEQUATE AIR CONDITIONER PERFORMANCE (COOLING SYSTEM SUSPECTED)
  1. Radiator and/or air conditioning condenser is restricted, obstructed or dirty.
  2. Electric radiator fan not operating when A/C is on.
  3. Engine is overheating (heat may be transferred from radiator to A/C condenser). High underhood temperature due to engine overheating may also transfer heat to A/C components.
  1. Remove restriction and/or clean as necessary.
  2. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
  3. Correct overheating condition.
INADEQUATE HEATER PERFORMANCE.
  1. Has a diagnostic trouble code (DTC) been set?
  2. Coolant level low.
  3. Obstructions in heater hose fittings at engine.
  4. Heater hose kinked.
  5. Water pump is not pumping coolant to heater core. When the engine is fully warmed up, both heater hoses should be hot to the touch.
  1. (Refer to the Appropriate Diagnostic Information)
  2. (Refer to DIAGNOSIS AND TESTING ) Repair as necessary.
  3. Remove heater hoses at both ends and check for obstructions. Repair as necessary.
  4. Locate kinked area and repair as necessary.
  5. (Refer to DIAGNOSIS AND TESTING - WATER PUMP ) Repair as necessary.
HEAT ODOR
  1. Various heat shields are used at certain driveline components. One or more of these shields may be missing.
  2. Is temperature gauge reading above the normal range?
  3. Radiator fan operating incorrectly.
  4. Has undercoating been applied to any unnecessary component?
  5. Engine may be running rich causing the catalytic converter to overheat.
  1. Locate missing shields and replace or repair as necessary.
  2. Refer to the previous Temperature Gauge Reads High in these Diagnostic Charts. Repair as necessary.
  3. (Refer to DIAGNOSIS AND TESTING ) Repair as necessary.
  4. Clean undercoating as necessary.
  5. (Refer to the Appropriate Diagnostic Information) Repair as necessary.
POOR DRIVEABILITY (THERMOSTAT POSSIBLY STUCK OPEN). GAUGE MAY BE READING LOW
  1. For proper driveability, good vehicle emissions and for preventing build-up of engine oil sludge, the thermostat must be operating properly. Has a diagnostic trouble code (DTC) been set?
  1. (Refer to the Appropriate Diagnostic Information) Replace thermostat if necessary.
STEAM IS COMING FROM FRONT OF VEHICLE NEAR GRILL AREA WHEN WEATHER IS WET, ENGINE IS WARMED UP, RUNNING, AND VEHICLE IS STATIONARY. TEMPERATURE GAUGE IS IN NORMAL RANGE.
  1. 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 contact the hot radiator, steam may be emitted. This usually occurs in cold weather with no fan or airflow to blow it away.
  1. Occasional steam emitting from this area is normal. No repair is necessary.
COOLANT COLOR
  1. Coolant color is not necessarily an indication of adequate corrosion or temperature protection. Do not rely on coolant color for determining condition of coolant.
  1. Check the freeze point of the coolant. (Refer to DIAGNOSIS AND TESTING ) Adjust the glycol-to-water ratio as required.
COOLANT LEVEL CHANGES IN COOLANT RECOVERY CONTAINER
  1. Level changes are to be expected as coolant volume fluctuates with engine temperature. If the level in the container was between the MIN and MAX marks when the engine was cold, the level should return to within that range after operation at elevated temperatures.
  1. A normal condition. No repair is necessary.
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