There are two basic ways for a WP to leak: 1) The shaft seal/bearing is bad and lets the coolant past the seal and out a weep hole. 2) The housing wasn't sealed properly when the pump half with the impellar was changed. This would be caused by either remains of the old gasket not being removed, damage to the new gasket when installed, reusing the old gasket, not removing the old gasket and putting on a new one (total of two gaskets).
I would suggest taking off the plastic shroud and observing where the leak is coming from. It could also be one of the hoses in the WP area.
