You can't fill a Legend cooling system without bleeding it, so you never actually got it filled completely. Given that, it will overheat every time.
First thing to do is make sure it's full of fluid and see if it continues to overheat. The bleed valve is just left of the thermostat housing. Open it up and let it flow until it's clear of bubbles, then continue to fill rad until full.
You can tell if the thermostat is opening by the flow. Also, check relative temps of upper and lower rad hoses (carefully with your hand) They should be similar, not too different temps.
Once full, fill the overflow bottle to the line and close the system up.
It should stay cool then. If not, verify the thermostat is opening.
Stock 1987 Legend LS Coupe 180k (11/07)