Todays Caller Dino, and his Neon percolating

Somehow I think the most likely cause was missed, and that being a defective radiator cap that is no longer holding pressure.

Several years back this same percolating had happened to my 95 Stratus with the 2.0 Neon engine in it, and a defective Radiator cap was all it was. Car is still going, pushing 160K.