Coolent leaking from my overflow valve on 98' Pontiac Grand Am?

Coolant started to leak but my car didn't overheat,
Was told it had to be my water pump, so replaced that,
Still leaking from the same place, next I changed out my thermostat,
Still leaking in the same place?

I can see that the overflow is connected the the firewall off the engine and the coolant flows through the whole engine without any problems except for this steady flow of water leaking from the car?

Any suggestions? Is there a quick fix?