Weird circumstances:

On the way home for work, the coolant light comes on.

So I watch the temperature gauge as I drive it to the nearest gas station, about two miles away, the temperature NEVER GOES UP from 90-C, stays steady (it's about 84-F and 70% humidity in Florida).

I finally get to the gas station, and feel the upper-radiator hose and there is NO pressure.

There is also no visual leaks or puddles of coolant anywhere.

I carefully remove the coolant-cap, and add some water, and drive to my destination another 3-miles away.

I park, and notice no leaks during my 30-minute pizza diversion.

I start the car, temperature is fine, and no coolant light, so I drive home another 3-miles.

When I get home, I pop the hood, and again there are no visible leaks, and the upper-radiator hose has NO pressure, hence I carefully remove the coolant-cap.

Then all of sudden medium-pressurized hot-coolant comes bubbling out, but not under the normal pressure.

I felt the thermostat bypass hose and it is hot, so it seems like the thermostat is working.

I know I need to pressure test it cool, but any ideas ?

Thanks,
:-) neil
1993 500E
(new hoses, radiator, thermostat about 3-years ago)