MBE 900 – Section 15.16 Low Coolant Temperature

Section 15.16
Low Coolant Temperature

There are several causes for low coolant temperature. These probable causes are:‪

• Faulty Thermostats
• Insufficient Radiator Air Circulation

Section 15.16.1
Troubleshooting Procedure for Faulty Thermostats

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

1. Remove thermostat from the thermostat housing; refer to "4.6.1 Thermostat Removal" .
2. Inspect thermostat for correct operation; refer to "4.6.1.1 Thermostat Checking" .
   1. If the thermostat is fully open at 95°C (203°F), check insufficient radiator air circulation; refer to "15.16.3 Troubleshooting Procedure for Insufficient Radiator Air Circulation" .
   2. If the thermostat is not fully open at 95°C (203°F), refer to "15.16.2 Thermostat Replacement" .

Section 15.16.2
Thermostat Replacement

Perform the following steps to replace thermostats:‪

1. Install new thermostat; refer to "4.6.2 Thermostat Installation" .
2. Verify replaced thermostat; refer to "15.16.2.1 Test Engine with New Thermostat" .

Section 15.16.2.1
Test Engine with New Thermostat

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

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked. ‪

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 82-105°C (180-221°F), no further troubleshooting is required. Shut down the engine.
   2. If the engine coolant temperature is not 82-105°C (180-221°F), shut down the engine. Check insufficient radiator air circulation; refer to "15.16.3 Troubleshooting Procedure for Insufficient Radiator Air Circulation" .

Section 15.16.3
Troubleshooting Procedure for Insufficient Radiator Air Circulation

To determine if insufficient radiator air circulation is causing low engine coolant temperature, visually examine the radiator and radiator shrouding.‪

1. If the radiator has excessive clogging, debris, or dirt, refer to "15.16.4 Exterior Radiator Repair" .
2. If the radiator shrouding is not damaged, incorrectly positioned, or inadequate, and if the radiator is absent of clogging, debris, and dirt, then call Detroit Diesel Customer Support Center at 313-592-5800.
3. If the radiator shrouding is damaged, incorrectly positioned, or inadequate, refer to "15.16.5 Radiator Shroud Repair" .

Section 15.16.4
Exterior Radiator Repair

Perform the following steps for exterior radiator repair:‪

1. Clean the exterior radiator of all clogging, debris, or excessive dirt; refer to OEM guidelines.
2. Verify exterior radiator repair; refer to "15.16.5.1 Test Engine with Repaired Exterior Radiator and Shrouding" .

Section 15.16.5
Radiator Shroud Repair

Perform the following steps for radiator shroud repair:‪

1. Repair or replace damaged radiator shrouding; refer to OEM guidelines.
2. Verify exterior radiator repair; refer to "15.16.5.1 Test Engine with Repaired Exterior Radiator and Shrouding" .

Section 15.16.5.1
Test Engine with Repaired Exterior Radiator and Shrouding

Perform the following steps to determine if exterior radiator or shrouding repair resolved the low engine coolant temperature:‪

PERSONAL INJURY ‪
To avoid injury before starting and running the engine, ensure the vehicle is parked on a level surface, parking brake is set, and the wheels are blocked. ‪

1. Start and run the engine.
2. Run the engine through its operating range with no-load condition for approximately five minutes, allowing the engine coolant to reach normal operating range.
   1. If the engine coolant temperature is 82-105°C (180-221°F), no further troubleshooting is required. Shut down the engine.
   2. If the engine coolant temperature is not 82-105°C (180-221°F), shut down the engine. Call Detroit Diesel Customer Support Center at 313-592-5800.