87 Fiero L4. I've tried two different Stant 180 degree thermostats. With the thermostat in place the temperature will rise quickly and the car will overheat. The radiator hose is cold, the hose in the rear of the car by the thermostat housing is really hot. I've bled the system a couple of times. If I remove the thermostat the problem seems to go away. In regular driving the car may reach 220, fan kicks in and temperature drops immediately. Any ideas? Thanks to all.
I was having the same kind of issue recently. Kept replacing the thermostat, and it still wouldn't kick on when it should have. My issue was that the gauge was reading incorrectly as it does for a lot of people here. I'm not sure how accurate yours is but that's what was wrong with mine at least. Is the temperature light turning on?
It did come close to overheating once, light came on but a hose had come loose. The main problem is with the thermostat in place there doesn't seem to be a flow from the rear of the car to the radiator. The hose by the thermostat housing is 'hot', the hose by the radiator is 'cold'. If I take the thermostat out both hoses get warm.
It is possible that the water pump impeller has detached from the shaft and is not spinning much. The symptoms you have would point in that direction, but it is a rare failure.