I have a 2001 Ford Taurus and it overheats. A mechanic flushed the system, replaced water pump, hoses and the thermostat, charged $$$ and it still overheats. I observed that when the engine heats up, the temperature indicator remains in its normal position but the fluid heats and can be seen bubbling...

Did you change the water pump? If you did, it could be something very serious...corroded and clogged water jackets. I'm assuming you changed the radiator because of rust. That rust may be inside the block, too. Also, you could have an issue with engine timing. Or even air in the system. Good luck...