1972 Mercury Cougar Car heats Up to much

Got white smoke coming out of the tail pipe? If so could mean a blown headgasket, cracked head or block-get it block and pressure tested. Fans coming On or fan clutch working properly.

Try bleeding the system could be air lock-

If it doesn't apply keep going. You didn't answer my Q is it? If not do below

BLEEDING COOLING SYSTEM

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.

Get the cooling system block and pressure tested