Never discount the simplest causes and easiest solutions.
I have to go back to the first responder Bubba 22349 because the cause and the solution was in his response.
Yesterday, after bleeding the system the day before, I went to the store and it started heating up quickly - city streets, light traffic, 8 miles +/-. When I parked the temp gun was reading 154 and it was puking coolant. I thought this ain't right. So on the way home I stopped and picked up a new cap.
Later when it cooled down, I went to see how much coolant I lost and check the cap. 4-5 oz is all. I got out the new cap to compare it with the old - the spring on the old seemed a pound or two lighter. I turned the caps over and lo and behold the rubber gasket at the bottom/top - depending on how you look at it - of the cap was gone - metal to metal does not make a great seal under pressure. It must have loosened and fell off, unbeknownst to me when I did a fluid check last week when I changed the oil. That's why the change in how it operated happened so suddenly an out of the blue.
Radiator Cap!
Simple, cheap and easy.
Don't over think the problem - I'm the worst offender.
Thanks to all who commented and all the good advise. Learned a few things I didn't know, and that, I'm sure, will come in handy in the future.
Charlie