SCREW 2H3906 - Caterpillar

Probable Causes
Plugged cooling fins for the radiator
Problems with the cooling fan
Extreme operating conditions
Water temperature regulator
Faulty radiator cap
Radiator
Faulty water pump
Low coolant level
Incorrect coolant mixture
Air in cooling system
Faulty temperature gauge
Faulty sending unit
Worn hoses or damaged hoses
Air inlet restriction
Exhaust restriction
Restriction of the shunt line
Restricted air flow through the aftercooler
Incorrect fuel setting
Incorrect fuel injection timingRecommended Repairs
Plugged Cooling Fins for the Radiator
Clean obstructions in cooling fins for the radiator.Problems With the Cooling Fan
Check for proper operation of the cooling fan. Check applicable drive belts, pumps, speed sensors, and/or solenoids for proper operation.Reduced airflow through the radiator can be caused by one of the following items:
Incorrect fan
Improperly positioned fan shroud
Damaged fan bladeThe fan must be large enough to send air through most of the area of the radiator core.Loose fan drive belts or loose water pump belts will cause a reduction in air and coolant flow. Tighten the belts to the proper tension. Refer to Specifications, "Belt Tension Chart".Extreme Operating Conditions
Determine if the engine is operating under extreme outside temperatures or high altitudes.When outside temperatures are too high for the rating of the cooling system, there is not enough temperature difference between the outside air and coolant temperatures.The cooling capacity of the cooling system goes down as the engine is operated at higher altitudes. A pressure type cooling system must be large enough to keep the coolant from boiling.Running an engine at lower engine speeds can cause the engine to lug. This low rpm causes a reduction in air flow through the radiator. The low rpm also causes a reduction in the flow of coolant through the system. This combination of less air and less coolant flow during high input of fuel will cause above normal heating.Water Temperature Regulator
A water temperature regulator that does not open completely can cause above normal temperatures. To test the water temperature regulator, refer to Systems Operation, Testing And Adjusting.Radiator Cap
A pressure drop in the radiator can cause the boiling point to lower. The lower boiling point could allow the cooling system to overheat. A pressure test of the cooling system may be used to check the cooling system pressure as well as the pressure cap relief valve. Ensure that the gasket sealing surface is clean and undamaged. If the cap fails the test, check the rubber seal on the cap as well as the operation of the pressure relief valve.Radiator
Clean the radiator and flush the radiator. Check for debris between the fins of the radiator core which prevents free air flow through the radiator core.A radiator that is undersized for an application will not effectively transfer the heat out of the cooling system. A radiator that is undersized will cause the engine to run at a temperature that is higher than normal. Make sure that the radiator is sized in accordance with the OEM specifications.Faulty Water Pump
A water pump that has a loose impeller, an eroded impeller, or a damaged impeller does not pump enough coolant for correct engine cooling. Remove the water pump and check for damage