Why does a 1990 Bronco II 2.9 2WD leak coolant just above and left of the thermostat or top radiator hose where a white plug attaches to the engine?

the v6 2.9 litre Ford motors cam,e with aluminum heads and after a few years of wear and tear and constant heat they tend to expand and contract until the warp or crack and no longer seal well causing them to leak or blow the motor.