When i drive for a short time, my engine over heats. on 1997 Buick Skylark

It starts to overheat after driving in town for just 3-5 minutes. Happens every time you drive it.
The heater core went out and i didn't fix it , they just re-routed it.

Asked by for the 1997 Buick Skylark
the problem may be compounded now that you are driving it overheated. it may have been just a t stat but now you may have damaged the motor internally.