I've just got a xj8 v8 3.2 1998 and have a problem finding out what this plug/sensor is to and for Can anyone help me find out what this is for and what is it please
Does this have anything to do with the sensor on other picture thanx
thanx in advance

 

It kinda looks like it could possibly be the coolant level sensor, which mounts up from underneath the reservoir. I can't remember what mine looked like, but that would certainly affect the 2nd picture if it is.

 

That's half of the coolant level sensor. The other half is still attached to the bottom of the coolant reservoir. If you reach underneath the forward inboard corner of reservoir you will find the remainder. If I remember correctly from changing mine you rotate it 90 degrees toward the fender and the piece will come out. It isn't necessary to drain the coolant. The sensor fits inside a tube that is dry from the reservoir.
Below is a picture of complete sensor.

 

That is someone's attempt at rigging the sensor to extinguish the warning.
You will likely need a new or replacement reservoir and level sensor.

bob