Pinpoint Test B: The Engine Overheats
Engine Cooling
Pinpoint Tests
Pinpoint Test B: The Engine Overheats
Normal Operation
The engine cooling system functions to maintain engine temperatures 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. From the coolant pump, coolant is sent through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core with coolant. The coolant pump is operated by engine rotation through a pulley which is driven by the accessory drive belt to circulate 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 is allowed to flow through the radiator circuit in order 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 proper 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.
For the coolant flow diagrams, refer to Engine Cooling Engine Cooling in the Description and Operation information.
- DTC P0217 (Engine Coolant Over Temperature Condition) - Indicates an engine overheat condition was detected by the Engine Coolant Temperature (ECT) sensor.
This pinpoint test is intended to diagnose the following:
- Low coolant level
- External engine coolant leak
- Air lock in system
- Pressure relief cap installation
- Restricted airflow through the A/C condenser or radiator
- Internal engine coolant leak
- Coolant condition/concentration
- Accessory drive components
- Non-OEM engine enhancement components
- Cooling fan
- Electronically actuated cooling fan clutch
- Radiator
- Thermostat
- Engine Coolant Temperature (ECT) gauge
- ECT sensor - primary cooling system
- Heater core
- Coolant pump
- Coolant flow restriction
- Engine oil in engine coolant
PINPOINT TEST B: THE ENGINE OVERHEATS
WARNING: Always allow the engine to cool before opening the cooling system. Do not unscrew the coolant pressure relief cap when the engine is operating or the cooling system is hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly. Failure to follow these instructions may result in serious personal injury.
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B1 CARRY OUT INSPECTION AND VERIFICATION
- Carry out the Inspection and Verification procedure. Inspection and Verification
- Were any concerns found?
Yes
REPAIR as needed. TEST the system for normal operation.
No
GO to B2.
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B2 CHECK FOR DTCs
- Check for DTC P0217.
- Is DTC P0217 present?
Yes
GO to B3.
No
Actual engine overheating has not been verified. CHECK the Engine Coolant Temperature (ECT) gauge operation. REFER to Instrumentation, Message Center, and Warning Chimes Testing and Inspection. If any other PCM DTCs are retrieved, REFER to Electronic Engine Controls - Diesel Engine P Codes for Electronic Engine Controls.
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B3 CHECK FOR NON-OEM ENGINE ENHANCEMENT COMPONENTS
- Check the engine for any non-OEM components
- Are there any non-OEM components on the engine?
Yes
ADVISE the customer the engine modifications may be causing the engine to overheat.
No
GO to B4
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B4 CHECK FOR AN AIRFLOW OBSTRUCTION
- Check the radiator or A/C condenser for an obstruction such as leaves or cardboard.
- Is an obstruction present?
Yes
REMOVE the obstruction. TEST the system for normal operation.
No
GO to B5.
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B5 CHECK THE ENGINE COOLANT LEVEL
NOTE: Allow the engine to cool before checking the engine coolant level.
- Ignition OFF.
- Visually check the engine coolant level in the degas bottle.
- Is the engine coolant level within specification?
Yes
GO to B6.
No
ADJUST the engine coolant level as necessary. GO to B6.
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B6 PRESSURE TEST THE ENGINE COOLING SYSTEM
- Pressure test the engine cooling system. Refer to Component Tests, Cooling System Pressure Test. Engine Cooling
- Does the engine cooling system leak?
Yes
REPAIR or INSTALL new components. TEST the system for normal operation.
No
GO to B7.
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B7 CHECK THE ENGINE COOLANT FOR AN INTERNAL LEAK
- Inspect the engine coolant in the degas bottle for signs of engine oil.
- Is engine oil evident in the coolant?
Yes
REFER to Engine - 6.7L Diesel Testing and Inspection for engine diagnosis.
No
GO to B8.
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B8 CHECK THE ENGINE OIL FOR COOLANT
- Remove the oil level indicator from the engine.
- Is coolant evident in the oil?
Yes
REFER to Engine - 6.7L Diesel Testing and Inspection for engine diagnosis.
No
GO to B9.
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B9 CHECK THE COOLING SYSTEM FOR COMBUSTION GASES
- NOTE: Use UView(R) Combustion Leak Tester part number UVU560000-R or equivalent.
- Using a cooling system combustion gas leak tester, following the instructions supplied with the tester, check the coolant for combustion gases.
- Are combustion gases present?
Yes
REFER to Engine - 6.7L Diesel Testing and Inspection for engine diagnosis.
No
GO to B10.
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B10 CHECK THE COOLING FAN CLUTCH OPERATION
- Ignition OFF.
- Check the cooling fan clutch operation. Refer to Computers and Control Systems.
- Is the cooling fan clutch operation OK?
Yes
GO to B11.
No
INSTALL a new fan clutch. TEST the system for normal operation.
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B11 CHECK THE COOLANT PUMP OPERATION
- Start the engine.
- Allow the engine to run for 10 minutes. Place the climate control function selector in the MAX HEAT position. Feel the heater outlet hose.
- Is the heater outlet hose hot?
Yes
GO to B12.
No
INSTALL a new coolant pump. TEST the system for normal operation.
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B12 CHECK THE THERMOSTAT OPERATION
- Start the engine.
- Allow the engine to run for 10 minutes. Feel the upper radiator hose.
- Is the upper radiator hose hot?
Yes
CHECK the engine coolant temperature gauge operation. REFER to Instrumentation, Message Center, and Warning Chimes Testing and Inspection.
No
GO to B13.
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B13 VISUALLY INSPECT THE THERMOSTAT
- Carry out the Thermostat Visual Inspection in the Component Tests information. Engine Cooling
- Is the thermostat damaged?
Yes
INSTALL a new thermostat. TEST the system for normal operation.
No
INSTALL a new thermostat. TEST the system for normal operation. If the engine still overheats, INSTALL a new radiator. TEST the system for normal operation.
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