Water sloshing noise

Air mixed into the cooling system creates the noise your describing.There is a specific procedure I'm not even getting into. Nissan has a special vacuum tool that will pull out the air. No more gurgling noise or water flowing noise in the car. It's NOT aimed at you but Nissan is the worst of the Asian manufactures curious how long they will survive.

Thank you for the explanation, do you think it's safe to drive until I have the air issue fixed?

Air can only mix in the cooling system if there is a leak,or you just filled the radiator without bleeding the system,and you can bleed the system your self, dont know what Auto_Centric is telling you but you can remove resivoir cap and add fluid to line with car running,let car heat up to warm tempreture and keep adding fluid as needed untill it holds to the full line,then lace cap on.This is the bleeding tech.

rain storm caused water to leak inside the door panels unplug bottom liner drain fixed. diagnosed by swinging doors to locate ones filled with water simple fix