[Expando1]

I have a 1990 Honda Civic, sedan, 1.5L, 130K miles which started to overheat yesterday. The temp gauge climbed to the red bar on 'Hot' then would intermittently drop to normal range for a moment before climbing back up over and over. So I figured it was the thermostat getting stuck and would intermittently open when the pressure got to a certain point hence the intermittent drop in the temp guage. Well I changed the thermostat and gasket today, refilled the fluid coolant level, and took it for a spin. Wouldn't you know it, within 3 blocks...same problem. Popped the hood, the radiator fans are blowing like mad and everything is hot. What else should I consider?