What was found
AFTER PUSHBACK AND BOTH ENGINES STARTED EQUIPMENT COOLING OVERBOARD VALVE FAULTED. FOLLOWED ECAM WHICH WAS TO TURN IT OFF. CHECK MEL-NOT FLAGGED ITEM. OVERBOARD VALVE WAS NOT USED BOTH PACKS OPERATING NORMALLY, CONTINUED FLIGHT. AFTER T/O, AIRCRAFT WOULD NOT HOLD PRESSERIZATION. TRIED MANUAL PRESSURIZATION, NO HELP. TRIED TO SLOW CLIMB, NO HELP. RETURNED TO IND, GOC TO MEM, NO PROBLEMS. AVI COOLING EXTRACTION VALVE IS STUCK FULL OPEN. REMOVED AND REPLACED OVERBOARD EXTRACT VALVE PER AMM 21-23-13-4, OPS CHECK GOOD.