That happened to me in West Yellowstone a couple of years ago. Luckily there was a Napa in town and of course they had a replacement. Thank god I wasn’t driving a Kia.Replaced coolant cap. Went to top off coolant after air worked out of the system after the heater hoses and connector replacement and the top of the old cap separated from the bottom. I think the o ring was hard. I was able to twist and pry it out with curved needle nose pliers.
View attachment 403558
View attachment 403559