Well, my friend's 98 Ex is doing something similar that needs the headgasket to be checked. Her cooling system seems to intermitently not work, usually driving down to NYC from CT, the gauge will start to go up and blah blah blah. We've had everything besides the waterpump replaced and we thought worse case was the headgasket. What my shop did to semi test the headgasket, was to put it on an emissions machine and run a carbon check(something like that) and this can sorta tell you if the gasket is going or gone. Hope you understood what I just said cuz I don't think I did. Good luck in anycase.