96 concrd water loss

here's the deal, changed the cam sensor and the belt tensioner. Car runs like a top no flutter or shake. Top off the radiator and start car. after 5-10 minutes fan starts to cycles like normal heat gauge is just below center line. shut car off pull rad cap water is up to the top. Then I drive the car around the block to the front of the house, heat gauge goes way up check the rad and its empty!!!!!! Fill it back up wait ten minutes start car everything fine. till i move the car then the water goes somewhere????? No white smoke, no contamination in the oil. Haven't yet run a comp test on each cylinder to see if one or more is weak. But car can just squeak the tires (not bad for a 6 with 140K miles) so i don't think its that but maybe.

any other ideas where the water is going. Don't want to pony up couple hundred for title and registration transfer if i can't fix this.

i would keep an eye on the oil condition. also, could the heater core be leaking? any puddles under the car? also check the water pump for possible leaks.