Yesterday my truck was acting fine. Got in at after a brief stop and it said engine coolant overheating. Shut it back off and checked everything. Reservoir is where it should be, no leaks seen anywhere. Turned key and temp showed normal. Called a buddy and he said limp it home. I was driving and it popped up again. Stopped and waited 5 minutes. Temp gauge normal again so i resumed. Popped up a third time and went into limp mode. This time i left it there overnight. Oil check shows it clean. Reservoir fine. Any ideas??

 

CHT (Cylinder Head Temperature) sensor could be going bad. They are not very robust. There is no actual coolant temperature sensor. The PCM uses the input from the CHT to provide an inferred coolant temperature to the IPC.

 

Have you done a coolant change/refill lately? I'm thinking about air pockets, if that's the case.

 

Unles you've done a coolant change very recently, looks like a sensor going bad.

 

The >>cylinder head<< temperature sensor is located in the rear of the passenger side head, in a blind hole.
It does not touch the coolant.
It is a 'dual' lead senor with two elements.
Once removed it has to be replaced with a new sensor because there is a shaft that has to rest against the bottom of the blind hole to make contact with the head material as it is tightened in place.
Best to get the DTC code to verify this.
The dash display only tells you what the system is but not the exact issue.
Good luck.

 

If the CHT sensor "goes bad", the PCM may think the engine is overheating. (Read your current DTC codes !!!) This the description of what happens to a 2015 2.7L when this happens. It may be similar to your 5.0L situation. MY 2015 Ford Work Shop Manual- "Stage 1 of the strategy commences if the engine starts to overheat. The CHT sensor transmits a signal to the PCM, which moves the temperature gauge pointer into the red zone. If the engine is not switched off and the temperature continues to rise, the Powertrain Check Lamp is illuminated. This indicates to the driver that the engine is approaching critical limits and should be stopped. At this point DTC P1285 is set in the PCM which can be retrieved using a scan tool. Stage 2 of the strategy commences if the lamp and temperature gauge are ignored by the driver. The PCM will start to control the engine by cutting out 3 cylinders and restricting load. The RPM will be limited below 3,000 RPM initially then will slowly be ramped down with time to as low as 800 RPM. Simultaneously the MIL illuminates. This indicates that long term engine damage can occur and vehicle emissions will be affected. At this point DTC P1299 is set in the PCM which can be retrieved using a scan tool. Air is drawn into the deactivated cylinders. This helps to control the temperature of the engine internal components. The deactivated cylinders are alternated to allow even cooling of all the cylinders. NOTE: If the driver is using a high percentage of throttle travel (for example, an overtaking maneuver) when the PCM starts engine deactivation (Stage 2), the deactivation will be delayed for 10 seconds. NOTE: After 3-cylinder operation has begun, the engine will not revert to 6-cylinder operation, even if the temperature should fall, until the ignition is switched off and then on again.NOTE: The MIL can only be extinguished by using a scan tool after the fault has been rectified and the DTC cleared.

Stage 3 of the strategy will commence if the engine temperature continues to rise. This results in the engine being totally disabled before major engine damage or seizure occurs. The Powertrain Check Lamp will begin to flash, indicating to the driver that the engine will be switched off after 30 seconds. This allows the driver time to choose a suitable parking place." Read your DTCs!!! Good Luck.

 

The CHT will only cause a DTC if it fails completely out of range. If it is just starting to go bad and hasn't completely failed it may read a high temperature without producing a DTC.

 

If as reported in post #1 "Popped up a third time and went into limp mode.", then I think a DTC would have been set.

 

You are correct.

 

CHT sensor info video. Should help with 5.0L location and such.