What was found
(CAN) AIR RETURN DUE TO PRESSURIZATION ISSUE,WAS AT APPROXIMATELY F080,OVERWEIGHT LANDING.NO EMERGENCY DECLARED. IAW AMM 05-51-11-200-004-A, VERTICAL SPEED 600 FT MIN OR MIN FOR OVERWEIGHT LANDING CREW REPORTS 200 FT MIN. NO FURTHER ACTION NECESSARY SERVICEABLE. SKIN AIR VALVE REPLACED IAW AMM 21-26-53 PB 401.