OK. I drove the VX until it was fully hot. Then I shut it down, thinking that it would build the most pressure right after it first stops. I took my high powered flashlight and dental-type inspection mirror and looked at everything I can think of. I can't find anything leaking anywhere. I slid a sheet of paper under the heater core. No leaks on the paper. Not sure where the coolant has been going. Someone suggested that there may be air-bubbles in the system that need to work their way out. Perhaps I should take it off-road and bounce it around for awhile. I snugged up the connections and refilled the reservoir. Hopefully it will stabilize...