Water pump

I have a 2001-200 bought new in Dec. 01. It has 247 miles on it. I have not ridden it or cranked it up since July, 2002. Last month, I noticed a small pool of antifreeze under it and investigated. I saw a small accumulation of antifreeze on the water pump drain bolt. I cleaned it off, tighetened all the associated hoses and made sure that the drain bolt was tight and checked it again in 2 days and the small accumulation was back. I checked closer and noticed that the water pump cover gasket has a slight amount of damage observable from the outside so I replaced it. When I took the cover off, the mating surface of the gasket looked good and it looked like the damage would not have caused a leak. I also made sure that the drain bolt washer was in place and looked good. A few days later the accumulation was back. I've checked everything I can to find a leak. There is no visible antifreeze trail to indicate a problem higher up somewhere. I noticed a small hole behind the drain bolt in the body of the water pump. What is its purpose? It has been around 0 degrees F at night, but the bike is inside the garage.

Any ideas?

Thanks,
Tim