Pinpoint Test B : The Engine Overheats: Notes

WARNING: This page is about a different car, the 2018 Ford F-550 Super Duty and 2018 Ford F-450 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.

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
Accessory drive components
Non-OEM engine enhancement components
Cooling fan
Cooling fan clutch
CHT sensor
Radiator
Thermostat
Coolant pump
Coolant flow restriction
Engine oil in engine coolant
Transmission fluid in engine coolant

Diagnostic Trouble Code (DTC) Fault Trigger Conditions

DTC	Description	Fault Trigger Conditions
P0217	Engine Coolant Overtemperature Condition	Sets in the PCM when an engine overheat condition was sensed by the CHT sensor.
P1285	Cylinder Head Overtemperature Condition	Sets in the PCM when an engine overheat condition was sensed by the CHT sensor.
P1299	Cylinder Head Overtemperature Protection Active	Sets in the PCM when an engine overheat condition was sensed by the CHT sensor. A failure mode effects strategy called fail-safe cooling was activated to cool the engine.