The MacBook worked OK until anything like streaming a video shut it down.
It was obvious that overheating caused the temperature sensor to shut it down.
And there was no sound of the fan, so I ordered the fan to repair it.
The repair went easily since I had been familiar with MacBook computers in the past.
The job took 2 hours with no problems.
In future, I'll take some pitches to share with others in the iFixit community.
Given the curiously to watch people working on anything like cars & equipment of course lead me to tear into things myself. While I worked on almost everything else, computers have only been in recent 20 years.
When I discovered iFixit, the step by step guides were the invaluable tool for the repair.
So if one has the "do it yourself" motive, sharing information with others is essential.