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Cooling System Diagnosis Chart

WARNING: This page is about a different car, the 2004 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
COOLING SYSTEM DIAGNOSIS CHART

CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS LOW
  1. Has a Diagnostic Trouble Code (DTC) been set indicating a stuck open thermostat?
  2. Is the temperature sending unit connected?
  3. Is the temperature gauge operating OK?
  4. Coolant level low in cold ambient temperatures accompanied with poor heater performance.
  5. Improper operation of internal heater doors or heater controls
  1. (Refer to POWERTRAIN DIAGNOSTIC PROCEDURES ) for On-Board Diagnostics and DTC information. Replace thermostat if necessary.
  2. Check the temperature sensor connector. Repair connector if necessary.
  3. Check gauge operation. (Refer to ENGINE TEMPERATURE GAUGE ). Repair as necessary.
  4. 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 RADIATOR PRESSURE CAP for WARNINGS and CAUTIONS associated with removing the radiator cap.
  5. Inspect heater and repair as necessary. (Refer to DIAGNOSIS AND TESTING - HEATER PERFORMANCE TEST ) for procedures.
TEMPERATURE GAUGE READS HIGH OR THE COOLANT WARNING LAMP ILLUMINATES. COOLANT MAY OR MAY NOT BE LOST OR LEAKING FROM THE COOLING SYSTEM
  1. 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.
  2. Is the temperature gauge reading correctly?
  3. Is the temperature warning illuminating unnecessarily?
  4. Coolant low in coolant reserve/ overflow tank and radiator?
  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 the radiator cap.
  7. 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
  8. Incorrect coolant concentration
  9. Coolant not flowing through system
  10. Radiator or A/C condenser fins are dirty or clogged.
  11. Radiator core is corroded or plugged.
  12. Dragging brakes
  13. Fuel or ignition system problems.
  14. Bug screen or cardboard is being, reducing airflow.
  15. Thermostat partially or completely shut.
  16. Viscous fan drive not operating properly.
  17. Cylinder head gasket leaking.
  18. Heater core leaking.
  1. 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 Possible Causes (No. 2-18).
  2. Check gauge. (Refer to DIAGNOSIS AND TESTING - INSTRUMENT CLUSTER ). Repair as necessary.
  3. (Refer to DIAGNOSIS AND TESTING - INSTRUMENT CLUSTER ).
  4. Check for coolant leaks and repair as necessary. (Refer to DIAGNOSIS AND TESTING ).
  5. Tighten cap
    1. Check condition of cap and cap seals. Refer to RADIATOR PRESSURE CAP . Replace cap if necessary.
    2. Check condition of radiator filler neck or degas bottle. If neck is bent or damaged, replace radiator or degas bottle.
    1. Check condition of radiator cap and cap seals. Refer to RADIATOR PRESSURE CAP . Replace cap if necessary.
    2. Check condition of radiator filler neck. If neck is bent or damaged, replace radiator.
    3. 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.
    4. Check coolant reserve/overflow tank and tanks hoses for blockage. Repair as necessary.
  8. Check coolant.
  9. 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.
  10. Remove insects and debris. (Refer to - STANDARD PROCEDURE ).
  11. Have radiator re-cored or replaced.
  12. Check and correct as necessary. (Refer to DISC )
  13. Refer to FUEL INJECTION or IGNITION CONTROL for diagnosis and testing procedures.
  14. Remove bug screen or cardboard.
  15. Check thermostat operation and replace as necessary. (Refer to ENGINE COOLANT THERMOSTAT ).
  16. Check fan drive operation and replace as necessary. (Refer to FAN DRIVE VISCOUS CLUTCH ).
  17. Check for cylinder head gasket leaks. (Refer to - DIAGNOSIS AND TESTING ).
  18. Check heater core for leaks. (Refer to HEATER CORE ). Repair as necessary.
TEMPERATURE GAUGE READING IS INCONSISTANT (FLUCTUATES, CYCLES, OR IS ERRATIC
  1. During cold weather operation, with the heater in the high position, the gauge reading may drop slightly.
  2. Temperature gauge or engine mounted gauge sensor defective or shorted. Also, corroded or loose wiring in this circuit.
  3. Gauge reading rises when vehicle is brought to a stop after heavy use (engine still running)
  4. Gauge reading high after re-starting a warmed up (hot) engine.
  5. Coolant level low in radiator (air will build up in the cooling system causing the thermostat to open late).
  6. Cylinder head gasket leaking allowing exhaust gas to enter cooling system causing a thermostat to open late.
  7. Water pump impeller loose on shaft.
  8. Loose accessory drive belt, (water pump slipping)
  9. Air leak on the suction side of the water pump allows air to build up in cooling system causing thermostat to open late.
  1. During cold weather operation, with the heater in the high position, the gauge reading may drop slightly.
  2. Check operation of gauge and repair if necessary. (Refer to DIAGNOSIS AND TESTING - INSTRUMENT CLUSTER ).
  3. A normal condition. No correction is necessary. Gauge should return to normal range after vehicle is driven.
  4. A normal condition. No correction is necessary. The gauge should return to normal range after a few minutes of engine operation.
  5. Check and correct coolant leaks. (Refer to - DIAGNOSIS AND TESTING ).
    1. Check for cylinder head gasket leaks. (Refer to - DIAGNOSIS AND TESTING ).
    2. Check for coolant in the engine oil. Inspect for white steam emitting from the exhaust system. Repair as necessary.
  7. Check water pump and replace as necessary. (Refer to WATER PUMP -3.7L/4.7L ).
  8. (Refer to ACCESSORY DRIVE ). Check and correct as necessary.
  9. 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
  1. Pressure relief valve in radiator cap is defective.
  1. Check condition of radiator cap and cap seals. (Refer to RADIATOR PRESSURE CAP ). Replace cap as necessary.
COOLANT LOSS TO THE GROUND WITHOUT PRESSURE CAP BLOWOFF. GAUGE 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 ).
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. Mixture is too rich or too lean.
  1. Check reason for overheating and repair as necessary.
  2. Check coolant concentration.
HOSE OR HOSES COLLAPSE WHILE ENGINE IS RUNNING
  1. Vacuum created in cooling system on engine cool-down is not being relieved through coolant reserve/overflow system.
    1. Radiator cap relief valve stuck. (Refer to RADIATOR PRESSURE CAP ). Replace if necessary
    2. Hose between coolant reserve/overflow tank and radiator is kinked. Repair as necessary.
    3. Vent at coolant reserve/overflow tank is plugged. Clean vent and repair as necessary.
    4. Reserve/overflow tank is internally blocked or plugged. Check for blockage and repair as necessary.
NOISY VISCOUS FAN/DRIVE
  1. Fan blades loose.
  2. Fan blades striking a surrounding object.
  3. Air obstructions at radiator or air conditioning condenser.
  4. Thermal viscous fan drive has defective bearing.
  5. A certain amount of fan noise may be evident on models equipped with a thermal viscous fan drive. Some of this noise is normal.
  1. Replace fan blade assembly. (Refer to RADIATOR FAN - VISCOUS )
  2. Locate point of fan blade contact and repair as necessary.
  3. Remove obstructions and/or clean debris or insects from radiator or A/C condenser.
  4. Replace fan drive. Bearing is not serviceable. (Refer to FAN DRIVE VISCOUS CLUTCH ).
  5. (Refer to FAN DRIVE VISCOUS CLUTCH ) for an explanation of normal fan noise.
INADEQUATE HEATER PERFORMANCE. THERMOSTAT FAILED IN OPEN POSITION
  1. Has a Diagnostic trouble Code (DTC) been set?
  2. Coolant level low
  3. Obstructions in heater hose/ fittings
  4. Heater hose kinked
  5. 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.
  1. (Refer to POWERTRAIN DIAGNOSTIC PROCEDURES ) for correct procedures and replace thermostat if necessary
  2. (Refer to DIAGNOSIS AND TESTING ).
  3. Remove heater hoses at both ends and check for obstructions
  4. Locate kinked area and repair as necessary
  5. (Refer to WATER PUMP -3.7L/4.7L ). If a slipping belt is detected, (Refer to ACCESSORY DRIVE ). If heater core obstruction is detected, (Refer to HEATER CORE )
STEAM IS COMING FROM THE, FRONT OF VEHICLE NEAR THE 1 GRILL AREA WHEN WEATHER IS WET, ENGINE IS WARMED UP AND 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 contacts 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. Adjust coolant mixture as necessary.
COOLANT LEVEL CHANGES IN COOLANT RESERVE/OVERFLOW TANK. TEMPERATURE GAUGE IS IN NORMAL RANGE
  1. 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.
  1. A normal condition. No repair is necessary.
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