After weeks of trying to find a unknown leak in my cooling system, the gremlin has finally appeared. It was the water pump. I kept smelling coolant when I stopped and got out of the car, but I never could find the problem.
When I was fueling up, I did my usual look underneath and saw a little stream dripping down from behind the fan. Half a day in the driveway and it's good as new and no leaks!
But thanks for the help along the way.

Pg