What was found
PHX - AIR TURNBACK - 2/25/01 - AFTER LEVELING OFF AT FL 310, FLIGHT ATTENDANTS REPORTED A BURNING SMELL IN THE CABIN; THE CREW STARTED A DESCENT AND TURNED OFF THE GRASPER FAN AND THE SMELL SEEMED TO GO AWAY; THE FLIGHT RETURNED TO PHX. IN PHX, MAINTENANCE FOUND OIL DRIPPINGS ON THE RT AIR CYCLE MACHINE (ACM); BOTH THE LT AND RT ACM''''S APPEARED TO BE OVERSERVICED; BOTH ACM''''S WERE DRAINED AND REFILLED; THE AIR CONDITIONING PACKS WERE RUN FOR 30 MIN AT MAX TEMPERATURE AND NO ODORS NOTED.