Ok so I have a 1986 f150 4x4 with a 302 the motor is not running really hot only about 180-195 so a little higher than my average temp i usually sit at 182 and never go higher. The problem is when I stop and turn my truck off antifreeze comes spewing out of the little hole in the top of the exansion bottle. I am not loosing any antifreeze going down the road and the truck is not smoking at all it just dumps it when I turn my truck off. Like when this first happened I was on a 200 mile trip and I never overheated. So for the ride home I just filled the radiator back up and drove home again it did not overheat just dumped when I stopped.

 

Radiator cap is likely bad.