Leaking coolant out of water pump overflow not weep hole?

Ok so I have a 02 grizzly 660 it immediately starts pouring coolant out when I try to fill the radiator. It comes out of the overflow on the water pump not the weep hole. This is if the quad is running otlr not. If I plug it it will come out of the overflow by the thermostat housing. Has new water pump and just rebuilt the top end. Any suggestions? Thanks in advance.