PLUG-CUP 3B0645 - Caterpillar

Conditions Which Generate This Code:The temperature of the engine coolant has exceeded the trip point. Refer to Troubleshooting, "Event Codes" for the trip point.System Response:The Electronic Control Module (ECM) will log the event.
Engine power is reduced.Test Step 1. Check the Engine's Cooling System
Verify that the cooling system is filled to the proper level. If the coolant level is too low, air will get into the cooling system. Air in the cooling system will cause a reduction in coolant flow.
Check the quality of the coolant. Follow the recommendations in the Operation and Maintenance Manual.
Check for air in the cooling system. Air can enter the cooling system in different ways. The most common causes of air in the cooling system are the incorrect filling of the cooling system and combustion gas leakage into the cooling system. Combustion gas can get into the system through inside cracks, a damaged cylinder head, or a damaged cylinder head gasket.
Check the cooling system hoses and clamps. Damaged hoses with leaks can normally be seen. Hoses that have no visual leaks can soften during operation. The soft areas of the hose can become kinked or crushed during operation. These areas of the hose can restrict the coolant flow. Hoses become soft and/or get cracks after a period of time. The inside of a hose can deteriorate, and the loose particles of the hose can restrict the coolant flow.
Check the sea water strainer for plugging.
Check the heat exchanger for a restriction to the flow of sea water.
Check the water pump. A water pump with a damaged impeller does not pump enough coolant. Remove the water pump and check for damage to the impeller.
Check 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. A restriction of the shunt line from the expansion tank to the inlet of the jacket water pump will cause a reduction in water pump efficiency. A reduction in water pump efficiency will result in low coolant flow.
If the cooling 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.
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.
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