I just replaced the radiator the thermostat and the sensor for the radiator and it still says it's overheating what else can it

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My car keeps on reading it's overheating and then it goes down and then it goes back up and it goes down and it goes back up then goes down I don't know what's wrong with it and someone please help me out cuz I change the thermostat I change the radiator and I change the temp sensor