The Nissan Path

My wifes 05 Pathfinder SE has some weird water draining/trickling/rushing from what sounds like behind the glovebox. Most noticeable when cold and when accelerating (change in pitch of vehicle?) Pathfinder is stock and has not had any major repairs required. Any ideas what it could be?

You need to burp your coolant. You're probably hearing air pockets traveling through your heater core. Jack up the front, turn the heat on high, open the radiator and add coolant as the air bubbles come out.

I tried this and it seemed to have helped. Thanks for the tip! I didn't jack up the front so I may have to do it again, but I cannot notice the sound now.