1997 Ford Taurus my car overheats when stopped.

Engine Cooling problem
1997 Ford Taurus 4 cyl Front Wheel Drive Automatic 130k miles

I have a 97 taurus. Sometimes my car will over heat if I stop at a light. I pulled over threw it in park and checked the fans but they were on. I took it home and replaced the thermostat. I bled the cooling system n refillied. I replaced two sensors. But the problem persists. It only happens if im stopped but if I but it in park and rev the gas peddle it quickly goes down. There is no fluid leaking. No loud noises. Nothing else unusual about my car im just worried. I have no idea whats wrong