Mazda 323 1984 overheats?

More info is needed, when does it overheat? sometimes, all the time, up hills, in city but o/k on hwy???? Symptoms help as well as recent work done.

But anyway,

Check to make sure the cooling fan comes on when the car is getting hot. If not check relay & sensor.

Check the coolant, is it full? Does it flow in the rad when hot(thermostat open). Be carefull not to scald yourself by opening hot rad under pressure!

Does the rad hose running from the thermostat housing stay cooler than the engine side (infared temp sensor makes this easier).

Is the rad in good shape?

Maybe remove the thermostat & check it for damage.