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It should not be driven with an overheat condition as it has the possibility of ruining an otherwise good engine. The air conditioning should be turned off to alleviate adding additional hot air from the A/C condensor to the radiator. The car heater should be turned on to act as an additional radiator and assist the one behind the grill. Is it really overheating or is it indicating an overheating condition? If it is indicating an overheat condition it could just be an engine temperature sensor or an engine coolant temperature sensor that has gone bad. Those are easy to replace and cheap also. If blowing coolant and thumping it is definitely overheating and should not be driven. If it is indeed overheating then it could be low coolant, thermostat failed closed, water pump not delivering, a lean fuel condition, or radiator partially plugged. Since the sensors are cheap and easy to replace I think I would change those first. Once that has been done then you can depend on the system to give you an accurate reading. If the indication is that the system is still obverheating then you can begin checking the radiator for partially plugged cross flow tubes. You do this after driving and then with the engine off by feeling the back side of the radiator and identifying any cool spots. The entire surface should be warm to the touch without any cool spots. Cool spots indicate a plugged tube and a no flow condition. Next move on to the thermostat and change it along with the antifreeze solution. If still overheating then I would suspect the waterpump. After that I would suspect a lean fuel condition brought on by partially plugged injectors or bad Oxygen sensors, or low fuel pressure. What repair action has the Toyota dealer already done? Has it been throwing any DTC's, Digital Trouble Codes? Have you serviced the antifreeze at least every three years and generally kept the system maintained?
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