1999 overheating

The car does not overheat at below 60 mph and the coolant level remains at the correct level. But if i drive between 65-70mph for a period of time the engine starts to rev at higher RPM's and then overheats?? Pressure tested as fine??

Does the engine rev at a higher speed because it drops out of overdrive? What is the level and condition of the transmission fluid? Does your car have a separate transmission cooler, or is it part of the radiator? Which engine and transmission does your Taurus have?

There have been a lot of people who've experienced bad impellars on the water pump, but that would seem unrelated to causing the engine run faster.

When you say it overheats, does it actually overheat, or you're just going off the temp gauge? I'm guessing the latter since the coolant level remains correct. When you pull over due to temperature, are the cooling fans behind the radiator running?

-Rod

It has the standard 3.0 v6 with automatic
It does drop out of overdrive when it revs up. The Trans. fluid level is fine.
Not sure about a separate Cooler for the trans.

It does really overheat. It blew the old cap off and then the new one also.. Then when I refill it, and keep running under 60 mph the coolant level stays fine. Engine runs and shifts great at the 60 mph?? The problems comes up at that 70mph mark.

There are two 3.0 engines that come "standard" The Vulcan and Duratech. First thing I would do is assure that the radiator and rest of the internals are clean. Hard water in the coolant mix can cause the core of the radiator to grow obstructions.
Cooling fans don't run at higher ground speeds, computer shuts them off.
If it is overheating enough to blow the coolant cap off, you are flirting with severe engine damage.