2006 pontiac montana overheating only in the winter season, summer season no probler
the coolant flow should be noted, one can take a lazer thermometer at the entrance and exit points on the radiator, no coolant flow = fins eaten off the waterpump~ would go with an expensive model that won't degrade~
of course the standard operating temperature is 280 degrees~ if the thermostat is full of corrosion and is sluggish to open...perhaps in winter only would probably get a new t-stat and replace with correct coolant~
Odd. Check the coolant level and purge air out of the cooling system. Maybe the thermostat is at fault?