Leaking cooling fluid

Hi, I have a '91 chevy s-10 blazer. 4.3 L 153,000 miles. I drove to the bank the other day and when i came out there was a puddle of lime green fluid under my car. i made sure that it was in fact coming from my car. I drove home and checked again and it was still dripping. i looked inside and it felt like there was a hole in the lower radiator tube. i went and replaced that and filled the radiator back up. i went and test drove it to make sure every thing is working. when i came back i looked under the car and it was dripping again. i looked under the car and down inside and it seems to be dripping from where the belt is. i did more driving and i noticed that it doesnt really start dripping until i put the car in park and turn it off. when i am driving and stopped in one spot for a minute. then i reversed to see if there was a puddle. there wasnt. is there anyway you can tell me whats up? thanks