Start simple. Clean your rad, and check the fill level.
If you can smell fluid, then you are losing fluid. Low fluid, introducing air into the system, or a combo of both will cause overheating issues.
I'd say you more then likely have both.
4.0's trap air easily because of their length. To really get a good bleed of the cooling system raise the front, and run it until the thermostat opens. Watch your overflow bottle for bubbles, and make sure there is some coolent in there when you are doing.
You can bleed with the cap off, but watch out, when the stat opens, it will gurgle a hot mess and drain down the front. If you get some air and gurgling like that, repeat the same step cap on, with fluid in the overflow bottle.
A 4.0 with a good condition cooling system should never need a taurus on high speed unless it being worked hard on a trail at very low speeds on a very hot day, or the rad is clogged up.