[slovcan]

Originally Posted by RogerHeinz57

Are you running a KV6 powered vehicle ?

If you are, here is something to check that only takes a moment -
Remove the cover that the oil filler cap sit over, take a look with a torch if possible, and take a look at the gaps between the alloy manifold pipework at the "V" area.
Is there a pool of coolant laying at the bottom ?
If yes, then either the thermostat or it's seal may have let go, and the mist from the boiling coolant may have sprayed over the engine temperature sensor causing the panic at the dash panel gauge and red warning light to display. This being the case, the cause of the puddle underside is because the "V" section of the engine has a small drain / port hole allowing fluids to drain out. The hole is behind where the water pump housing is and the flow will end up on the road just by the inside of the drivers side front wheel.
My ZT 190 has done this, the thermostat has sprung a leak at one of the connectors for a hose to fit on.
Not enjoying the repair, but taking my time and cleaning everything up to a good state prior to re-assembly.

Hope this may help you get to the bottom of your mystery !

I just checked his profile. It's a 1.8T.