940152 Volvo.Penta Hexagon nut

System Response:The Electronic Control Module (ECM) logs the event. The ECM will transmit a warning to the display in the cab. The ECM will reset the event when the coolant temperature falls below 105 °C (221 °F) for more than four seconds.Possible Performance Effect:
Low powerTroubleshooting:Test Step 1. Check the Engine
Check the cooling system for problems.
Verify that the cooling system is filled with coolant to the proper level. If the coolant level is too low, air may be allowed to enter the cooling system. Air in the cooling system will cause cavitation and a reduction in coolant flow.
Check the quality of the coolant. Refer to the Operation and Maintenance Manual for coolant recommendations.
Check for air in the cooling system. Air can be introduced into the cooling system in different ways. The most common cause of air in the cooling system is the improper filling of the cooling system. Refer to the Operation and Maintenance Manual for the proper filling procedure for your engine.The next likely cause is combustion gas leakage into the cooling system. Combustion gas can be introduced into the cooling system through damaged liner seals, cracks in the liners, a damaged cylinder head, or a damaged cylinder head gasket.
Check the cooling system hoses and clamps for damage. Clamps that are damaged and hoses that are leaking can usually be discovered during a visual inspection.Hoses that have no visual leaks can soften during operation. The soft areas of the hose can kink or the soft areas of the hose may collapse during operation. This can restrict the coolant flow. This can cause the engine to overheat. Check the hoses for soft spots.Internal cracks can also develop in cooling system hoses. This type of deterioration usually produces particles that can build up in the cooling system. This may cause a restriction in the coolant flow through components. Check the hoses for spots that are hard or brittle.
Check the water pump. Remove the water pump and check for damage to the impeller. A water pump with a damaged impeller will not pump an adequate amount of coolant through the system.
Check the operation of the water temperature regulator. A water temperature regulator that does not open, or a water temperature regulator that only opens part of the way can cause overheating.
If the cooling system for this application is equipped with an expansion tank, check the shunt line for the expansion tank. The shunt line must be submerged in the expansion tank. If the shunt line is not submerged, air will be introduced into the cooling system.Check the shunt line for a restriction. A restriction of the shunt line from the expansion tank to the inlet of the water pump will cause a reduction in water pump efficiency. A reduction in water pump efficiency will result in low coolant flow.
High air inlet temperatures can cause high cooling system temperatures. Check for a problem in the engine's air inlet and exhaust systems.
Check for a restriction in the air inlet system. A restriction of the air that is coming into the engine can cause high cylinder temperatures. High cylinder temperatures cause higher than normal temperatures in the cooling system.
Check for a restriction in the exhaust system. A restriction of the air that is coming out of the engine can cause high cylinder temperatures.
If the air inlet system for this application is equipped with an aftercooler, check the aftercooler. A restriction of air flow through the air to air aftercooler can cause overheating. Check for debris or deposits which would prevent the free flow of air through the aftercooler.
The engine's operating conditions can also affect cooling system temperatures. Check the operating conditions of the engine.
Consider high ambient temperatures. When ambient temperatures are too high for the rating of the cooling system, there is not enough of a temperature difference between the ambient air and coolant temperatures.
Consider high altitude operation. The cooling capability of the cooling system is reduced at higher altitudes. A pressurized cooling system that is large enough to keep the coolant from boiling must be used.
The engine may be running in the lug condition. When the load that is applied to the engine is too large, the engine will run in the lug condition. When the engine is running in the lug condition, engine rpm does not increase with an increase of fuel. This lower engine rpm causes a reduction in coolant flow through the system. Expected Result:A thorough inspection of the engine revealed the cause of the high cooling system temperature.Results:
OK - The cause of the high cooling system temperature has been identified.Repair: Repair the problem. Ensure that the repair eliminates the original problem.STOP