Pinpoint Test B : Pinpoint Test: Notes

The Engine Overheats 

Normal operation and Fault Conditions 

The engine cooling system maintains the engine temperature during operation. Correct coolant flow through the engine, radiator and remainder of cooling system passages and components is essential to maintaining a correct engine temperature.

Engine coolant flows primarily from the engine to the radiator circuit and back to the coolant pump. Coolant is sent from the coolant pump through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core with coolant. The coolant pump circulates the coolant. The coolant thermostat is a control valve actuated by coolant temperature. When the thermostat is closed, coolant flow bypasses the radiator circuit and returns to the coolant pump. When the thermostat is opened, coolant flows through the radiator circuit to transfer engine-generated heat to the outside air.

Engine overheating generally occurs when there is a disruption in the ability to control either coolant flow at the correct rate, the inability to transfer heat from the engine through the coolant (including low coolant) or an inability to transfer engine-generated heat to the outside air through the radiator.

Possible Sources 

• Low coolant level
• External engine coolant leak
• Airlock in system
• Pressure relief cap installation
• Restricted airflow through A/C condenser/radiator
• Internal engine coolant leak
• Coolant condition/concentration
• Non-OEM engine enhancement components
• Electric cooling fan
• ECT sensor
• Radiator
• Thermostat
• Temperature gauge
• Coolant pump
• Coolant flow restriction
• Active grill shutter

Diagnostic Trouble Code (DTC) Fault Trigger Conditions