overheating

I just replaced the timing belt and water pump. Also the auto tension-er and pulleys. This was because one day it lost all its coolant and immediately overheated. Belt did not break. After installing parts in the timing belt kit and putting everything back together i put coolant in it and it started right up. I let it idle and it started to overheat. i turned it off and saw a coolant leak under the front drivers side. Also, i could hear a boiling sound. It is very hard to determine exactly where the leak is coming from.