I have a consistent but puzzling coolant leak. I drive to work (27 miles), go out at lunch, and back home (another 27 miles) or just comparable weekend driving. After I park it - no leak. Check later that night - no leak. Check it again in the morning - no leak. Leave it setting, drive something else to work and check it when I get home - leak. It only leaks a little, about a 5-6 inch diameter circle and nothing more. It's definitely antifreeze and the only place I see any is in the bottom of the radiator housing directly under the fan where it appears to pool up and then leaks to the ground. It will do this every time I drive it if I leave it setting the next day. Any ideas?