Help! 2006 f250 overheat mystery

[boscoe99]

Yes, the thermoswitch closing will set the over temperature alarm. No disagreement on that at all.

Insofar as one function of oil is to act as a coolant, and insofar as the sensor is measuring block/oil temperature, then I suppose it could be called a coolant temperature sensor. I wouldn't but...

Here what Yamaha data says about the F250 engine temperature sensor (thermosensor) and its effects:

[fairdeal]

Rodbolt must be having a "senior moment"

Now that I see those docs, it reminds me -

I KNOW I've read HIS posts,

of using resistors to check that the themosensor alarm works

[rodbolt17]

no senior moments, I have actually watched it.

to PROPERLY test the system you short the pink and black AND short the SENSOR leads with the resistor,
HOWEVER
if just the SWITCH closes and the ECT is normal there is a delay in the alarm .
but when the alarm sounds there is no visual indicate..

this I have watched on YDS.

and its the typical sign of an ex stack failing.

why the wide temp spread between the ECT and the switchs, dunno, I did not design it.
other than the SENSOR has a main function or giving the ECU information on block temp for fuel control.
the switch has a main,only,function of telling the ECU its simply to hot.

[James1234]

UPDATE: Got the engine back last week- powerhead had to come off. cooling passages blown out twice - success! small obstruction cleared. From what I am told, it does not take much to clog the passages. Shop ran the motor for a LONG time in idle in the tank - no overheat.

Appreciate all the help!