I have a 1997 f-150 4.6
it has 397000 miles the water temp gauge isn't working properly it shows c then it jumps to hot and shuts down
never over heats
can happen at anytime
has any one exp this
Ed

 

It's been 7 days without a reply so here is my thoughts.
The lead may be shorting against the block at some point or the sensor is faulty.
The sensor is located under the intake manifold into the driver side head.
The lead to it should be visible from the front of the head leading back under the intake.
A second lead in that area is to the intake manifold tuning motor.
Your fault could affect drivability by 'falsely' triggering the computer into 'Limp mode' action.
Good luck.