You're not going to like my diagnosis..........
You have a bad head gasket.
Your symptoms match what my car was doing after TU in Mammoth.
Water loss with no visible leeaks.
Water temp spiking way above the thermostat limit then settling back down.
Smoke or steam in exhaust.
After replacing head gaskets, all of those symptoms were gone on my car.
Take the car to somebody with an exhaust gas sniffer. Have them remove the
radiator cap and stick the probe in the tank. If you get an HC reading you
have your confirmation.
> Any further comments or ideas out there?
> Steve Sage