NOTE: For operation in cold or very cold temperatures, a winterfront cover or radiator shutters are recommended.
Probable Cause(s):
* Long Idle Periods
* Very Light Loads
* Water Temperature Regulator
* Air Vent Valve
* Fan Clutch Engaged
1. Long idle periods:
When the engine is running with no load, only a small quantity of fuel is burnt and engine heat is removed too fast.
2. Very light load:
Very light loads can cause below normal heating because of the low heat input of the engine. A slight restriction of air flow through the radiator will help to correct this problem.
3. Water temperature regulator:
A water temperature regulator that is “stuck” open (will not move to the closed position) will cause below normal heating. A regulator that is stuck between the open and closed positions, or a vent valve that is stuck open, can cause below normal coolant temperatures when the engine has a light load.
4. Air vent valve:
An air vent valve located in the water temperature regulator that is stuck open, can cause below normal coolant temperatures when the engine has a light load. If fan clutch remains engaged when it should release, overcooling may occur.
5. Fan clutch engaged:
a. Check coolant temperature sensor. Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting SENR6566, for Engine Sensor Open or Short Circuit Test.
b. Check exhaust brake circuit. Make repairs as necessary.