Two weeks ago I was on my way to work in my 1992 Nissan D21.I noticed I wasn't getting the full power when I stepped on the accelerator. A few minutes Later I head a loud pop then, the biggest cloud of white steam started coming out of my engine. I pulled over tried to start the truck, looked under the hood and the engine was covered with coolant and it wouldn't start. Then after work that day the truck started up and I moved it. I have been able to drive it around since with no problem, except, the thermostat isn't reading the temperature.
Doesn't sound like a head gasket....Check the Engine via the Oil filler hole for signs of water...Any white sludge and your head gasket is gone.
However, if its not the head gasket, sounds like your cooling system is blocked or constricted and /or your temperature gauge is not working. You could have gunk clogging the system anywhere in the Engine cooling network including the radiator - but the radiator is usually obvious. Can you see the water flow with the rad. cap off when the Engine is hot? If not - something is blocked - perhaps a hose but more likely in the head somewhere.
Can you get a cooling system flush by experts? Not too expensive....
(NB: No temperature reading is also a sign of NO water)