95 Mustang 3.8 overheating

[dr_jones2u]

I have a high mileage 95 Mustang that started overheating last night. I replaced the radiator last week and its been fine until now. Checked the fluid level, there is no thermostat (it was removed last winter when the radiator began giving me problems.) Until yestrday the temp gauge barely got to midway in the Normal range (dead center of the gauge). What I noticed this morning is that it seems fine until I have to accelerate then the gauge rises when I reach speed and let off it waits a few seconds then the gauge drops back down to near the normal range. The fan seems to take a long time to start, in fact Im not sure it does start all the time. Do I have a loose impeller or something? Ive never really ever been able to see much wwater moving. Is it possible that I have air in the systema nd it just took this long to show up?