Car overheating

If this only occurs in city driving or at slow speeds, check if the radiator fan is turning on. That is not needed at highway speeds.

If the fan is working, have your mechanic perform a chemical test at the coolant reservoir to check for a leaking cylinder head gasket. That involves drawing air from the cooling system, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are sneaking into the cooling system, the liquid will turn bright yellow.