Usage:
Overheating
Abnormal Cooling System
1. Defective Temperature Gauge
If the temperature gauge shows that the coolant temperature is above normal and all other conditions indicate that conditions are normal, check the coolant temperature in another method, such as:
- * Read the coolant temperature with an ECAP or DDT.
- * Install an 8T0470 Thermistor Thermometer Group
- * Install a temperature sensitive tape.
- * Install a new gauge that is known to be good.
- * Install an 8T0470 Thermistor Thermometer Group
2. Defective Coolant Temperature Sensor
If a fault is detected in the coolant temperature sensor circuit, determine if the fault is in the wiring or the coolant temperature sensor following the procedure in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Repair or replace parts as needed. The coolant temperature sensor should be accurate within plus or minus 3° C (6° F). Check the accuracy of the sensor if it is found to be out of specification.
3. Low Coolant Level
Low coolant level can cause overheating to occur. Low coolant level can be caused by leaks in the cooling system or by improper filling of the radiator. With the engine cool, the coolant level should be at the low end of the fill neck on the radiator. If the coolant is below this level, a visual inspection should be done to see if any leaks can be seen. If nothing obvious is seen, refer to the topic Loss Of Coolant in this section. Fill the radiator according to recommendations in the Operation & Maintenance Manual.
4. Dirty Radiator
Check for debris between the fins of the radiator core which could restrict the free flow of air through the radiator core. Also check for debris or deposits on the inside of the core which could restrict the free flow of coolant through the radiator. Clean out any debris that is found.
5. Fan Belt Slippage
Check for proper fan speed with the fan engaged. Check the belt tension. Check the belt tensioner bearing and spring for proper operation. Check the belt and pulleys for lubricant contaminants which could cause belt slippage. Check the belt for hardening and glaze caused by heat and slippage. Repair or replace any defective parts that are detected.
6. Defective Hoses
Check the hoses for leaks, cuts and loose clamps. Check for any hoses that are collapsed or restricted that could cause a decrease in the amount of flow of coolant through the engine or radiator. Replace as necessary.
7. Defective Pressure Cap
Inspect the sealing surface of the pressure cap and the radiator. Look for any damage to the seal or the sealing surface. Remove any foreign material and replace any defective seals. Check the sealing pressure of the cap with the Cooling System Pressurization Pump Group, 9S8140. This will check the opening pressure of the cap. If the cap is defective, replace it.
8. Shutters Not Functioning Correctly
Check the opening temperature of the shutters. The shutters must be completely open at a temperature below the fully open temperature of the water temperature regulator.
9. Defective Water Temperature Regulator
If the water temperature regulator is not opening properly it can cause the engine to overheat. Check the water temperature regulator for proper operation according to the test procedure for the thermostat located in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR3909.
10. Defective Water Pump
Check the water pump impeller for damage or looseness on the shaft. Also, see the topic, Cooling System, in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR3909.
11. Air In The Cooling System
Air in the cooling system reduces the heat transfer from hot engine parts to the coolant and causes low coolant flow. The most common causes of air are:
- * Improper filling of the cooling system trapping air in the system.
- * Combustion gas leaking into the system. If air is present in the cooling system, the engine should be checked for internal cracks (cylinder head, cylinder liner, spacer block) or for a defective cylinder head gasket.
The cooling system can be checked for air using the BOTTLE TEST. The equipment needed to do this test is a one pint bottle, a bucket of water, and a hose which will fit the end of the overflow pipe of the radiator.
Before testing, be sure the cooling system is filled correctly. Use a wire to hold the relief valve in the radiator open. Put the hose over the end of the overflow pipe. Start the engine and operate it at high idle rpm for a minimum of five minutes after the engine is at normal operating temperature. After five or more minutes at operating temperature, place the loose end of the hose in the bottle filled with water. If the water gets out of the bottle in less than forty seconds, there is too much exhaust gas leakage into the cooling system. Find the cause of the air or gas getting into the cooling system and correct as necessary.
12. Incorrect Fan, Fan Or Shroud Not In The Correct Position
The fan and shroud must be in the proper position to provide adequate flow of air to the radiator. The fan must be large enough to pull air through most of the area of the radiator core. Make sure the fan size, fan shroud, and position of the fan and shroud are according to the recommendations of the Truck Manufacturer.
13. Radiator Too Small
Check the recommendations of the Truck Manufacturer to be sure that the radiator is the proper size for the current power setting of the engine.
14. Air Restriction In The Engine Compartment
Check to make sure the filters, air conditioners, and other equipment are mounted in the engine compartment in such a way that they do not interfere with the flow of air into and out of the compartment.
15. High Outside Temperature
If there is not a large enough difference between the outside air temperature and the coolant temperature, the cooling system may not be capable of cooling the engine. To get better cooling, the truck can be operated in a lower gear to increase the speed of the cooling fan and the water pump, or a reduced vehicle speed to reduce the HP requirement.
16. Operation At High Altitude
The boiling point of the coolant decreases as the altitude the vehicle is operated at increases. Proper cooling system pressure must be maintained to prevent the coolant from boiling. If the truck is going to be used at a higher altitude for extended periods of time, a higher pressure radiator cap should be used.
17. Engine Used At A Lug Condition
"Lugging" the engine causes the engine rpm and fan rpm to operate slower. Low engine rpm will cause a reduction in coolant flow and air flow that may cause the engine to overheat. If the engine temperature is rising into a critical area, downshift the truck to a lower gear to provide increased engine rpm.
18. Air Inlet Restriction
Restriction of the air coming into the engine causes higher cylinder temperature and raises the temperature of the coolant. Check for a restriction in the system. See the topic, Restriction Of Air Inlet And Exhaust, located in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR3909.
19. Exhaust Restriction
A restriction in the exhaust will cause the engine temperature to increase due to higher cylinder temperatures. Make a visual inspection of the exhaust system to check for damaged piping or for a defective muffler. If no damage is found, the system should be checked for excessive back pressure. The back pressure must not exceed 1016 mm (40 in) of water. A simple visual check can be made by disconnecting the exhaust pipe from the turbocharger. Run the engine with the pipe disconnected to see if the problem has been corrected.
20. Fuel Injection Timing Not Correct
Check and make the necessary adjustments to the fuel injection timing. See the topics, Engine Test Procedure Number P-402, [Checking Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)] and Engine Test Procedure Number P-403, [Calibrating Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)], in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.
21. Shunt Line Restriction
Check for restriction in the shunt line from the radiator top tank to the water pump. A restriction can cause a lower coolant flow and overheating.
22. Transmission Problems
Verify that the power-shift or automatic transmission is in proper adjustment and is operating properly as per the manufacturer's Service Manual. A transmission that is out of adjustment will cause additional heat to be transferred to the engine cooling system.
23. Faulty Fan Clutch
Check to verify that the fan clutch is engaging properly. Refer to the Truck Manufacturer's Service Manual for the proper procedure.
24. Engine Power Set Too High
Make sure the radiator size complies with the Truck Manufacturer's recommendations for the current engine power setting. Check the power settings of the engine with an ECAP to make sure they agree with the specification plate.
Overcooling
25. Defective Temperature Gauge
If the temperature gauge shows that the coolant temperature is below normal and all other conditions indicate that conditions are normal, check the coolant temperature in another method, such as:
- * Read the coolant temperature with an ECAP or DDT.
- * Install an 8T0470 Thermistor Thermometer Group
- * Install a temperature sensitive tape.
- * Install a new gauge that is known to be good.
- * Install an 8T0470 Thermistor Thermometer Group
26. Defective Coolant Temperature Sensor
If a fault is detected in the coolant temperature sensor circuit, determine if the fault is in the wiring or the coolant temperature sensor following the procedure in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Repair or replace parts as needed. The coolant temperature sensor should be accurate within plus or minus 3° C (6° F). Check the accuracy of the sensor if it is found to be out of specification.
27. Long Idle Periods
Running the engine for extended periods of time under no load conditions will cause the engine heat to be removed at a faster rate than it is being generated.
28. Very Light Loads
Very light loads, very slow speeds, or downhill travel can cause below normal heating due to the decreased amount of fuel that is being burned. The installation of shutters will help correct this problem by decreasing the flow of air into the engine compartment.
29. Defective Water Temperature Regulator
If the water temperature regulator is stuck open, it will cause below normal engine heating. To test the thermostat, see the topic, Testing The Cooling System, in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR3909.
30. Faulty Fan Clutch (Will Not Disengage)
Check for proper operation of the fan clutch. Refer to the Truck Manufacturer's Service Manual for the proper procedure.
31. Vent Line Open
If the vent line (OEM) between the temperature regulator and the radiator top tank is open, overcooling could result. Install a valve assembly in the line that will allow air venting but restrict coolant flow with the engine running.