PIN 8G5428 - Caterpillar

Use this procedure in order to troubleshoot a low coolant temperature. Refer to Troubleshooting, "Event Codes" for information about event codes. Access the monitoring system on Caterpillar Electronic Technician (ET) in order to view the current trip points for these codes.Probable Causes
Extreme ambient temperatures
Light loads
Low engine speed
The cooling fan is always on
Faulty water temperature regulator
The auxiliary coolant heater is faulty
The temperature sensor is faultyRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps     Values     Results    
1. Extreme Ambient Temperatures
Extreme ambient temperature can cause overcooling.
   
Extreme Ambient Temperatures    
Result: Ambient temperatures are extreme.
Repair: Install winter covers. Ensure that the problem is resolved.
Result: Ambient temperatures are not extreme.
Proceed to Test Step 2.    
2. Load Factor
Light loads can cause overcooling. This overcooling is caused by the low heat input of the engine.
   
Light Loads    
Result: Engine is operating under a light load.
Repair: Increase load factor if possible. Ensure that the problem is resolved.
Result: Engine is not operating under a light load.
Proceed to Test Step 3.
   
3. Low Engine Speed
Low engine speed can cause overcooling.
   
Low Engine Speed    
Result: Engine is running at a low speed.
Repair: Increase engine speed if possible. Ensure that the problem is resolved.
Result Engine is not running at a low speed.
Proceed to Test Step 4.
   
4. The Cooling Fan is Always On
If the cooling fan is always on, overcooling can occur.
   
Fan Always On    
Result The cooling fan is always on.
Repair: Resolve the issue. Ensure that the problem is resolved.
Result The cooling fan is not always on.
Proceed to Test Step 5.
   
5. Water Temperature Regulator
A regulator that is stuck open can cause overcooling.
A. Test the water temperature regulator according to Testing and Adjusting, "Water Temperature Regulator - Test".
B. Make sure that the proper water temperature regulator is installed. Refer to the Specifications manual for the correct water temperature regulator.
   
Water Temperature Regulator    
Result The regulator is stuck open or not installed.
Repair: Replace the regulator. Ensure that the problem is resolved.
Result The regulator not is stuck open is installed.
Proceed to Test Step 6.
   
6. Auxiliary Coolant Heater (if equipped)
A malfunctioning auxiliary coolant heater can cause low coolant temperature.
A. Determine if the engine is equipped with an auxiliary coolant heater.
B. Check the heater for proper operation.
   
Auxiliary Coolant Heater    
Result The coolant heater is not operating properly.
Repair: Replace the heater. Ensure that the problem is resolved.
Result The coolant heater is working properly.
Proceed to Test Step 7.
   
7. Faulty Coolant Temperature Sensor and/or Circuit
A. Check the reading of the coolant temperature on the Cat ET. The temperature should rise steadily as the engine is warmed. Ensure that the temperature is reasonable.    
Faulty sensor or cir