Q: My reservoir is boiling is that indication of needing a thermostat 2007 Nissan Pathfinder

Hi there - while it is possible that the thermostat is keeping your engines operating temperature too high (coolant temp gauge should always be in the middle of the gauge), the steam and boiling water out of the reservoir could also indicate that the radiator is simply not getting rid of engine heat as effectively as it should be. In either case, there is enough latent heat in the engine to boil coolant to steam as you are experiencing. I recommend an engine overheating inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.