BTW, I got your e-mail @Stuman but my reply says undeliverable. Not sure if it actually went through or not, but based on your pic, I'd say you had a trapped air bubble, or several small ones that accumulated, and have now purged out of the system, leaving the radiator low. Top off your radiator, make sure you have a little in your overflow (make it 2" or so just for good measure) and give it a shot. You may have to repeat a time or two, but that should do the trick.