My temperature gauge stays in the lower half of the gauge and then in 10 second or less the gauge goes past the red all the way over. I changed the thermostat, to be on the safe side and changed both temperature sensors and it still does it. The engine does not appear to be overheating, there's no smell or steam. The water pump was replaced less than 2 years ago and the radiator is good. The fluid levels are good. What could it be?
Try replacing your radiator cap and refilling/"burping" the system. If the pressure changes abruptly that can change the boiling point of the coolant and possibly cause an abrupt change in the temperature. A bad radiator cap could also allow air into the system which could make it appear that the system is full because the radiator and expansion tank are full, but really there are air pockets inside the water jackets or tubing.