coolant light temp show hot on 1995 Mercury Mystique

coolant light stays on temp gauge shoots up instantly, car has been checked by two different shops and they say they cant find anything wrong, car stalls at stop lights, smells hot but fluids all full. just had speedometer and cable replaced

Asked by for the 1995 Mercury Mystique
Either the engine is getting too hot or not. Narrow that down first by measuring engine coolant temperature with a diagnostic tool. Then, start pin pointing towards what is failing.