Waterpump

Hello folks I own a 71 New Yorker and I have been noticing lately that my 440 has been releasing coolent through the overflow hose on my rad. Recently I had changed all the belts on the car including the one that goes around the water pump it's not over or undertightend but since then it's started spitting out coolest but only when I shut the car off and not alot but enough .How does one know if the water pump is failing obviously if it's getting hot on a regular basis but these cars...

Waterpump
Author: big block