I recently bought this car from a neighbor, who warned me that it overheated, but I had bled the system and the car ran fine. Thinking the problem was dealt with I redid two bearings and all the struts, about $500 for everything, but now the overheating is back.
The car runs really well with no problems for about 5 miles, then all of the sudden, the temperature will slam up to the red like the thermostat closes. I've done my research and everything points to a blown head gasket, which would make sense, but the engine was recently replaced and none of the other signs are showing. There are no bubbles in the reservoir, no corrosion on the radiator cap, no excessive white smoke, the oil is perfect, and there is no extreme loss of coolant.
Is there any other reason that the thermostat would randomly close like this?