Thanks for the tip. If it starts leaking again, I'll check it out. Perhaps one of the hose clamps is loose. Whatever it was, it seemed to have something to do with the radiator cap. After this problem had been going on for a while, I went to unscrew the cap and it fell apart. I got a replacement cap and the problem mostly went away. It currently is using the amount of coolant it takes to go from the MIN mark to the MAX mark every 2,500 - 3,000 miles.