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Cooling System Diagnosis Chart - Diesel Engine

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.

Establish what driving conditions caused the complaint. Abnormal loads on the cooling system such as the following may be the cause:

  1. PROLONGED IDLE, VERY HIGH AMBIENT TEMPERATURE, SLIGHT TAIL WIND AT IDLE, SLOW TRAFFIC, TRAFFIC JAMS, HIGH SPEED OR STEEP GRADES.
    1. Idle with A/C off when temperature gauge is at end of normal range.
  2. TRAILER TOWING:

    Consult TRAILERING under TOWING in owner's manual. Do not exceed limits.

  3. RECENT SERVICE OR ACCIDENT REPAIR:

    Determine if any recent service has been performed on vehicle that may effect cooling system. This may be:

    • Engine adjustments (incorrect timing)
    • Slipping engine accessory drive belt
    • Brakes (possibly dragging)
    • Changed parts (incorrect water pump)
    • Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).
    NOTE: If investigation reveals none of the previous items as a cause for an engine overheating complaint, refer to COOLING SYSTEM DIAGNOSIS-DIESEL ENGINE  .

    These charts are to be used as a quick-reference only.

    COOLING SYSTEM DIAGNOSIS-DIESEL ENGINE

    CONDITION POSSIBLE CAUSES CORRECTION
    TEMPERATURE GAUGE READS LOW 1. Diesel engines, due to their inherent efficiency are slower to warm up than gasoline powered engines, and will operate at lower temperatures when the vehicle is unloaded. 1. The low gauge reading may be normal. See DIAGNOSIS AND TESTING - THERMOSTAT  .
    - 2. Is the temperature gauge connected to the temperature gauge coolant sensor on the engine? 2. Check, the engine temperature sensor connector in the engine compartment.
    - 3. Is the temperature gauge operating OK? 3. Check gauge operation. Repair as necessary.
    - 4. Coolant level low in cold ambient temperatures accompanied with poor heater performance. 4. Check coolant level in the coolant tank. Inspect system for leaks. Repair leaks as necessary. Refer to COOLANT  for WARNINGS and precautions before removing the pressure cap.
    - 5. Improper operation of internal heater doors or heater controls. 5. Inspect heater and repair as necessary. Refer to HEATING & AIR CONDITIONING for procedures.
    TEMPERATURE GAUGE READS HIGH. COOLANT MAY OR MAY NOT BE LOST OR LEAKING FROM 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) temperature and the air conditioning is on. Higher altitudes could aggravate these conditions. 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 normal range, determine the cause for the overheating and repair.
    - 2. Temperature gauge reading incorrectly. 2. Check gauge. Refer to INSTRUMENT CLUSTER .
    - 3. Coolant low in coolant tank and radiator. 3. Check for coolant leaks and repair as necessary.
    - 4. Pressure cap not installed tightly. If cap is loose, boiling point of coolant will be lowered. 4. Tighten cap.
    - 5. Poor seals at pressure/vent cap. 5. (a) Check condition of cap and cap seals. (b) Check condition of coolant tank filler neck. Make sure it does not leak pressure.
    - 6. Freeze point of antifreeze not correct. Mixture may be too rich. 6. Check antifreeze. Adjust antifreeze-to-water ratio as required.
    - 7. Coolant not flowing through system. 7. Check for coolant flow in coolant tank with engine warm and thermostat open. Coolant should be observed flowing through the tank. If flow is not observed, determine reason for lack of flow and repair as necessary.
    - 8. Radiator or A/C condenser fins are dirty or clogged. 8. Clean debris from radiator or A/C condenser
    - 9. Radiator core is corroded or plugged. 9. Have radiator re-cored or replaced.
    - 10. Aftermarket A/C installed without proper A/C condenser. 10. Install proper A/C condenser.
    - 11. Dragging Brakes. 11. Check and correct as necessary.
    - 12. Non-factory bug screen is being used reducing air flow. 12. Only a factory screen should be used.
    - 13. Thermostat partially or completely shut. This is more prevalent on high mileage vehicles. 13. Check thermostat and replace if necessary.
    - 14. Cylinder head gasket leaking. 14. Check cylinder head gasket for leaks.
    - 15. Heater core leaking. 15. Check heater core for leaks. Repair as necessary.
    TEMPERATURE GAUGE READING IS INCONSISTENT (FLUCTUATES, CYCLES OR IS ERRATIC) 1. During cold weather operation, with the heater blower in the high position, the gauge reading may drop slightly. Fluctuation is also influenced by loads, outside temperature and extended idle time with diesel engines. 1. A normal condition. No correction is necessary.
    - 2. Temperature gauge or engine mounted gauge sensor defective or shorted. Also, corroded or loose wiring in this circuit. 2. Check operation of gauge and repair as necessary.
    - 3. Gauge reading rises when vehicle is brought to a stop after heavy use (engine still running). 3. A normal condition. No correction needed. Gauge should return to normal range after vehicle is driven.
    - 4. Gauge reading high after starting a warm-up (hot) engine. 4. A normal condition. No correction needed. Gauge should return to normal after a few minutes of engine operation.
    - 5. Coolant level low in the coolant tank (air will build up in the cooling system causing the thermostat to open late). 5. Check and correct coolant leaks.
    - 6. Cylinder head gasket leaking allowing exhaust gases to enter the cooling system causing the thermostat to open late. 6. (a) Check for cylinder head gasket leaks with a commercially available leak tester. (b) Check for coolant in engine oil. Inspect for white steam emitting from exhaust system. Repair as necessary.
    - 7. Water pump impeller loose on shaft. 7. Check water pump and replace as necessary.
    - 8. Loose accessory drive belt (water pump slipping). 8. Check and correct as necessary.
    - 9. Air leak on the suction side of the water pump allowing air to build up in the cooling system causing the thermostat to open late. 9. Locate leak and repair as necessary.
    PRESSURE CAP IS BLOWING OFF STEAM AND/OR COOLANT. TEMPERATURE GAUGE READING MAY BE ABOVE NORMAL BUT NOT HIGH. COOLANT LEVEL MAY BE HIGH IN COOLANT TANK 1. Pressure relief valve in pressure/vent cap is defective. 1. Check condition of pressure/vent cap and cap seals.
    - 2. Head gasket leak or cracked cylinder head. 2. Repair as necessary.
    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 cooling system and repair as necessary.
    HOSE OR HOSES COLLAPSE WHEN ENGINE IS COOLING 1. Vacuum created in cooling system on engine cool-down is not being relieved through pressure/vent cap. 1. Cap relief valve stuck. Replace if necessary.
    NOISY FAN 1. Cooling fan blades loose. 1. Replace cooling fan assembly.
    - 2. Cooling fan blades striking a surrounding object. 2. Locate point of fan blade contact and repair as necessary.
    - 3. Air obstructions at radiator or A/C condenser. 3. Remove obstructions or clean debris from radiator or A/C condenser.
    INADEQUATE AIR CONDITIONER PERFORMANCE (COOLING SYSTEM SUSPECTED) 1. Radiator and/or A/C condenser is restricted, obstructed or dirty (insects, leaves, etc.) 1. Remove restriction or clean debris from radiator or A/C condenser.
    - 2. Engine is overheating (heat may be transferred from radiator to A/C condenser. High Under hood temperatures due to engine overheating may also transfer heat to A/C condenser). 2. Correct overheating condition.
    - 3. The cooling system is equipped with air seals at the radiator and/or A/C condenser. If these seals are missing or damaged, not enough air flow will be pulled through the radiator and A/C condenser. 3. Check for missing or damaged air seals. Repair as necessary.
    - 4. Is the Cooling fan operating correctly? 4. Refer to RADIATOR FAN - ELECTRIC  for diagnosis. Repair as necessary.
    INADEQUATE HEATER PERFORMANCE. MAY BE ACCOMPANIED BY LOW GAUGE READING 1. Diesel engines, due to their inherent efficiency are slower to warm up than gasoline powered engines, and will operate at lower temperatures when the vehicle is unloaded. 1. The lower gauge reading may be normal.
    - 2. Coolant level low. 2. Pressure test cooling system. Repair leaks as necessary.
    - 3. Obstruction in heater hose fitting at engine. 3. Remove heater hoses and check for obstructions. Repair as necessary.
    - 4. Heater hose kinked. 4. Locate kinked area. Repair as necessary.
    - 5. Water pump is not pumping water to 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. The accessory drive belt may also be slipping causing poor water pump operation. 5. Refer to WATER PUMP  . Repair as necessary. If a slipping belt is detected, refer to DRIVE BELTS  . Repair as necessary.
    HEAT ODOR 1. Various heat shields are used at certain drive line components. One or more of these shields may be missing. 1. Locate missing shields. Repair or replace as necessary.
    - 2. Is temperature gauge reading above the normal range? 2. Refer to the previous Temperature Gauge Reads High in these Diagnostic Charts. Repair as necessary.
    - 3. Has undercoating been applied to any unnecessary components? 3. Clean undercoating as necessary.
    STEAM IS COMING FROM FRONT OF VEHICLE NEAR 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 air flow to blow it away. 1. Occasional steam emitting from this area is normal. No repair is necessary.
    COOLANT ODOR 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. Refer to COOLANT  for antifreeze tests. Adjust antifreeze-to-water ratio as necessary.
    COOLANT LEVEL CHANGES IN COOLANT 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 HOT and COLD marks at normal engine operating temperature, the level should return to within that range after operation at elevated temperatures. 1. This a normal condition. No repair necessary.
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