Overheating

Given the age and mileage, a leaking cylinder head gasket is a good suspect. Your mechanic can perform a chemical test at the radiator to verify that. The test involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.

You can also borrow this tool from an auto parts store that rents or borrows tools, but they will make you buy your own bottle of fluid. That is because it is rendered ineffective if it freezes or if it becomes contaminated with antifreeze. They do not want to risk borrowing it to you with contaminated fluid. That is why they made the last person buy their own bottle of fluid. It can be less expensive to just pay your mechanic to do this test. It just takes a few minutes.

You might also consider adding a small bottle of dark purple dye to the coolant, then you check a day or two later with a black light. All auto parts stores will have the dye for the fluid you are checking, and those that borrow tools should have a black light. This dye also shows up as a bright yellow stain that you can follow back to the source. If the head gasket is leaking, you will find the bright yellow inside the tail pipe.

Here is a dandy article that explains more about head gaskets and leak-checking them:

https://www.2carpros.com/articles/head-gasket-blown-test

Another real common symptom of a leaking head gasket is white smoke from the tail pipe. Here is an article that describes that:

https://www.2carpros.com/articles/white-smoke-or-steam-coming-from-the-exhaust-pipe

Dandy. That is far better than a leaking cylinder head gasket, but do not expect this to be a permanent repair. When a hole has corroded through the radiator, it is just a matter time before more leaks show up. I tried soldering the holes in the radiator in my old rusty trusty minivan years ago. I gave up after pulling it out nine times in four months to fix nine holes. Can you imagine how my customers would feel toward me if I tried to fix their vehicles that way? Replace the radiator before the overheating does take out the head gasket.