Toyota Repair: Engine coolant overheating in a 93 camry, engine coolant, coolant

Question
I recently noticed that after about 15 minutes of driving at normal speeds of 20-40 MPH the car begins to smoke. when inspecting under the hood i notice the smoke coming from a few cracks (on top) in the engine coolant container. I took it to a mechanic who informed me that the container needs to be replaced. that may be the cause for the smoke, but the gauge inside the car indicates its still overheating. What should i do. thanks in advance!!!

Answer
The coolant overflow bottle may have cracks but it is not the cause of the overheating or did you mean there are cracks in the top of the radiator?
Overheating can have many causes from a simple one like a stuck thermostat to something more serious like a clogged up radiator or a blown headgasket, take the car to someone else and have it diagnosed for the overheating condition.