Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If there is an overheat warning, there may be dust influencing the heat sensors. Dust accumulates on cooling surfaces over time, and can diminish the cooling effect of air circulation.
Also check the airflow, quite simply, of all the fans.
So, I advise cleaning out, quite thoroughly, of all air passages, and especially of all heat-sinks and their surfaces. And also, checking the action of all fans, and the replacement of any fan not spinning at less than an adequate speed.
Let me know what you find out in doing so, and what your thoughts are. And I will advise you further.