Coolant Leak

I have a 2000 Ford Explorer XLT with 146,000 miles and a 5.0L V8 engine. About a year ago a began to notice a very small coolant leak under my vehicle periodically. A small puddle would be visible for a day or two and then the symptom would disappear for several days to a week. Then it would return. After a few months I took it to the dealership and they told me the thermostat housing was cracked. They replaced the housing, thermostat, and houses. Cost $400, but the problem dissappeared. About 6 months later, the problem returned again. After about a month, ironically my radiator cracked and was replaced $368. However, the original problem still exist and seems to be getting worse. It only appears to leak overnight in the garage and sometimes appears to be a large puddle. I crawled under the vehicle again today and it appears that the coolant is leaking almost all around the oil pan where it mounts to the engine. Today the puddle under my vehicle was almost the perfect shape of about half way around the oil pan. I am familiar with engines but not an expert. Is it possible that coolant is leaking from this area? The puddles are always clean and light green in color. I am unable to see any other wet area above the oil pan, just on the exhaust, where fluid has dropped from the oil pan area. Any help that would allow me to avoid another costly visit to the dealership would be great.