radiator hole and catastrophic overheating without warning

Just for the record.....the GR engines are aluminum block and heads

 

My bad then.

However, a warped block diagnosis w/o pulling a head is pretty much a stretch.

And $20k is a rugged price.

 

Truth

 

In for the skid fail pics showing the weak point to the radiador. I hope you get this taken care of OP.

 

Temp sensor cannot read temps if not immersed in water/coolant. If the gauge drops to cold, you have a BIG problem and it needs to be shut down immediately. Been like that forever.

It's one reason idiot lights for temps suck.

 

No you are the only guy who thinks this. At work we say "no matter how much you idiot proof something they will always make a better idiot".

The sensor measures the temperature of the coolant. The coolant transfers the heat of the engine to the coolant and then to the radiator and then to the air. A simple heat exchanger. Without the coolant as the heat transfer medium the system can not do its job and the motor well it can suffer all sorts of heat related issues as yours did.

The actual sensor uses resistance to measure the temperature. At different temperatures the resistance changes which is what gets converted to a gauge reading. So a lack of coolant may have it drop and then rise as it gets some coolant or drop as it does get coolant. End result is they often go wonky jumping around before they stabilize again at whatever temperature the actual sensor is at. So while it says X temperature the motor has no coolant and is overheating. IT REQUIRES COOLANT TO READ ACCURATELY.

Ignorance of how things work doesn't mean it isn't doing what it was designed to do.