I also have a coolant leak which I've tracked down to a leak between the top and bottom halves of the expansion tank. It's a very small leak with minimal loss - approx 1/2 gallon of coolant since the beginning of the year. But it's readily apparent - there is coolant residue on the tank originating from the seam. I'm nearly due for an Insp 2, and I'll get the tank replaced then.