Does anybody have any idea why the temperature gauge on a car will always go all the way up before dropping back to normal> the car a toyota avensis 1996 model doesnt overheat but anytime the car is started except for first thing in the morning the temperature gauge will go all the to the red zone then gradually drop to half the mechanic recomended we change the thermostat, water pump and sensors but the problem still persists now he is saying we should change the radiator from single cell to double does anyone have any idea whats causing the problem?