^I’m with him.
My 95 winter beater has had a blown headgasket all winter.,
when I mat the accellerator the temp drops to nothing, I replaced waterpump,thermo, and sensor, it still does it.
Nissan tech i consulted suggested the above 3 prior to saying it very well could be a headgasket.
it may be okay, may not. check coolant and oil levels.