819601A 1 Force DECAL-Top Stripe (MAXUM)

1. Defective Temperature GaugeIf 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.2. Defective Coolant Temperature SensorIf 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 LevelLow 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 RadiatorCheck 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 SlippageCheck 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 HosesCheck 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 CapInspect 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 CorrectlyCheck 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 RegulatorIf 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 PumpCheck 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 SystemAir 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 PositionThe 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 SmallCheck 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 CompartmentCheck 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 TemperatureIf 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