2015 Ed... Engine too hot warning popped up on my dash and I pulled over and it immediately cooled with engine running with just the fan blowing at highway speeds it overheats quickly but running at 40 to 60 mph it stays around the 230 temp range any faster and it immediately climbs I stoped to get coolant but when I cracked the cap on the overflow to slowly releas pressure it bubbled and level came up to the full line and then slowly seeped down back to the radiator just trying to find a diagnosis