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MBE 900 HIGH ENGINE COOLANT TEMPERATURE

There are several causes for high engine coolant temperature. These probable causes are: ‪

  • Improper Engine Coolant Level
  • Insufficient Radiator Air Circulation
  • Faulty Pressure Control Cap
  • Defective Coolant Hoses
  • Fan Belt is Incorrectly Adjusted
  • Inoperative Thermo-Modulated Fan
  • Faulty Thermostats
  • Faulty Water Pump
  • Combustion Gases in Coolant
  • Abnormal Radiator Coolant Flow

Troubleshooting Procedure for Improper Engine Coolant Level

To determine if improper engine coolant level is causing high engine coolant temperature, perform the following: ‪

  1. Visually inspect the radiator coolant level; refer to OEMguidelines.
    1. If the radiator coolant level is within approximately 50 mm (2.0 in.) of the radiator filler neck, check for insufficient radiator air circulation; refer to section .
    2. If the radiator coolant level is not within approximately 50 mm (2.0 in.) of the radiator filler neck, refer to section .

Improper Coolant Level Resolution

Perform the following steps to resolve improper coolant level: ‪

  1. Fill coolant system to correct level; refer to section .
  2. Verify coolant level resolution; refer to section .
Test Engine with Proper Coolant Level

Perform the following to determine if proper coolant level resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check for insufficient radiator air circulation; refer to section .

Troubleshooting Procedure for Insufficient Radiator Air Circulation

To determine if insufficient radiator air circulation is causing high engine coolant temperature, perform the following: ‪

  1. Visually examine the radiator and radiator shrouding.
    1. If the radiator is absent of clogging, debris, and dirt, check the pressure control cap; refer to section .
    2. If the radiator has excessive clogging, debris, or dirt; refer to section .
    3. If the radiator shrouding is not damaged, incorrectly positioned, or inadequate, check the pressure control cap; refer to section .
    4. If the radiator shrouding is damaged, incorrectly positioned, or inadequate, refer to section .

Exterior Radiator Repair

Perform the following for exterior radiator repair: ‪

  1. Clean the exterior radiator of all clogging, debris, or excessive dirt; refer to OEMguidelines.
  2. Verify exterior radiator repair; refer to section .

Radiator Shroud Repair

Perform the following for radiator shroud repair: ‪

  1. Repair or replace damaged radiator shrouding; refer to OEMguidelines.
  2. Verify exterior radiator repair; refer to section .
Test Engine with Repaired Exterior Radiator and Shrouding

Perform the following to determine if exterior radiator and shrouding repair resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check the pressure control cap; refer to section .

Troubleshooting Procedure for Faulty Pressure Control Cap

To determine if a faulty pressure control cap is causing high engine coolant temperature, perform the following: ‪

  1. Perform coolant pressure control cap tests.
    1. If the cooling system pressure is less than or equal to 62 kPa (9 lb/in2 ), check the coolant hoses; refer to section .
    2. If the cooling system pressure is greater than 62 kPa (9 lb/in2 ), refer to section .

Pressure Control Cap Resolution

Perform the following steps to resolve faulty pressure control cap: ‪

  1. Remove and replace pressure control cap; refer to OEMguidelines.
  2. Install a new pressure control cap; refer to OEMguidelines.
  3. Verify pressure control cap repair; refer to section .
Test Engine with Replaced Pressure Control Cap

Perform the following to determine if exterior radiator repair resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is normal, no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not normal, shut down the engine. Check coolant hoses; refer to section .

Troubleshooting Procedure for Defective Coolant Hoses

To determine if defective coolant hoses are causing high engine coolant temperature, perform the following: ‪

  1. Visually examine cooling system hoses; refer to OEMguidelines.
    1. If cooling system hoses are not soft, deteriorated, collapsed, or have leaking connections, check the fan belts; refer to section .
    2. If cooling system hoses are soft, deteriorated, collapsed, or have leaking connections, refer to section .

Coolant System Hoses Replacement

Perform the following steps to resolve worn or damaged coolant system hoses: ‪

  1. Remove and replace damaged or worn coolant hoses as necessary; refer to OEMguidelines.
  2. Install new coolant hoses as necessary; refer to OEMguidelines.
  3. Verify replaced coolant system hoses; refer to section .
Test Engine with Replaced Coolant Hoses

Perform the following to determine if the new coolant hoses resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range, and visually examine replaced hoses for any leaks.
    1. If the engine coolant temperature is 82-105C (180-221F) and no leaks are found, no further troubleshooting is required.
    2. If the engine coolant temperature is 82-105C (180-221F) and leaks are found, repair the leaks; refer to section . Shut down the engine.
    3. If the engine coolant temperature is not 82-105C (180-221F) and no leaks are found, shut down the engine. Check fan belt; refer to section .

Troubleshooting Procedure for Fan Belt is Incorrectly Adjusted

To determine is a misadjusted fan belt is causing high engine coolant temperature, perform the following: ‪

  1. Check the auto tensioner for spring loading.
  2. Compare tension to belt specifications.
    1. If the belt tension is normal, check the thermo-modulated fan; refer to section .
    2. If the belt tension is not normal, refer to section .

Belt Tension Resolution

Perform the following steps to resolve incorrect belt tension: ‪

  1. Replace the auto tensioner as required.
  2. Verify belt tension resolution; refer to section .
Test Engine with Correct Belt Tension

Perform the following to determine if belt tension resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check thermo-modulated fan; refer to section .

Troubleshooting Procedure for Inoperative Thermo-Modulated Fan

To determine if an inoperative thermo-modulated fan is causing high engine coolant temperature, perform the following: ‪

  1. Test the thermo-modulated fan; refer to OEMguidelines.
    1. If the thermo-modulated fan is functioning correctly, check thermostats; refer to section .
    2. If the thermo-modulated fan is not functioning correctly, refer to section .

Thermo-moduluated Fan Replacement

Perform the following steps to replace inoperative thermo-modulated fan: ‪

  1. Replace inoperative thermo-modulated fan; refer to OEMguidelines.
  2. Verify thermo-modulated fan replacement; refer to section .
Test Engine with Replaced Thermo-modulated Fan

Perform the following steps to determine if thermo-modulated fan replacement resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C 180-221F(), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check thermostats; refer to section .

Troubleshooting Procedures for Faulty Thermostats

To determine if faulty thermostats are causing high engine coolant temperature, perform the following: ‪

  1. Remove thermostat from the thermostat housing; refer to section .
  2. Inspect thermostat for correct operation; refer to section .
    1. If thermostat is fully open at 95C (203F), check water pump; refer to section .
    2. If thermostat is not fully open at 95C (203F), refer to section .

Thermostat Replacement

Perform the following steps to replace thermostats: ‪

  1. Install new thermostat; refer to section .
  2. Verify replaced thermostat; refer to section .
Test Engine with New Thermostat

Perform the following steps to determine if thermostat replacement resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check water pump; refer to section .

Troubleshooting Procedure for Faulty Water Pump

To determine if a faulty water pump is causing high engine coolant temperature, perform the following: ‪

  1. Remove the water pump and inspect pump for failed shaft or rotor.
  2. Replace water pump if damaged.
Test Engine with Replaced Water Pump

Perform the following steps to determine if thermo-modulated fan replacement resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check combustion gases in coolant; refer to section .

Troubleshooting Procedure for Combustion Gases in Coolant

To determine if combustion gases in coolant is causing high engine coolant temperature, perform the following: ‪

  1. Perform a cylinder compression test.
    1. If test results are to specifications; check radiator coolant flow; refer to section .
    2. If test results are not to specifications, refer to section .

Cylinder Head Gasket Replacement

Perform the following steps to replace cylinder head gasket: ‪

  1. Remove and replace cylinder head gasket; refer to section .
  2. Verify new cylinder head gasket replacement; refer to section .
Test Engine with Replaced Cylinder Head Gasket

Perform the following to determine if cylinder head gasket replacement resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Check radiator coolant flow; refer to section .

Troubleshooting Procedure for Abnormal Radiator Coolant Flow

To determine if abnormal radiator coolant flow is causing high engine coolant temperature, perform the following: ‪

  1. Install a sight glass with string (both ends) to the radiator outlet hose near radiator and before fill and heater return lines; see Figure 24160 .

    Radiator Flow Check

  2. Start and run the engine at full load.
  3. Observe the string for flow and direction as well as the fill and bleed lines. Continue observation while varying the engine speed between 1800-2400 rpm.
    1. If a balanced coolant flow is observed in the sight glass, call Detroit Diesel Technical Service Group. Shut down the engine.
    2. If a balanced coolant flow is not observed in the sight glass, refer to section . Shut down the engine.

Abnormal Radiator Coolant Flow Resolution

Perform the following steps, as necessary, to resolve abnormal radiator coolant flow: ‪

  1. Correct bleed line size, refer to OEMguidelines.
  2. Correct fill line size or connector fitting size; refer to OEMguidelines.
  3. Correct restrictive top tank opening; refer to OEMguidelines.
  4. Correct location of standpipe; refer to OEMguidelines.
  5. Verify repairs made to correct abnormal radiator coolant flow; refer to section .
Test Engine with Resolved Radiator Coolant Flow

Perform the following to determine if thermo-modulated fan replacement resolved high engine coolant temperature: ‪

  1. Start and run the engine.
  2. Run the engine through its operating range with no-load for approximately five minutes, allowing the engine coolant to reach normal operating range.
    1. If the engine coolant temperature is 82-105C (180-221F), no further troubleshooting is required. Shut down the engine.
    2. If the engine coolant temperature is not 82-105C (180-221F), shut down the engine. Call the Detroit Diesel Technical Service Group.