What was found
AIRCRAFT WAS GROUNDED: FLIGHT CREW REPORTED THAT ON APPROACH AT IDLE SLIGHT FUMES NOTED. AT GATE WITH APU ON PACKS ON FUMES BECAME WORSE ON FLIGHT DECK AND IN CABIN. MAINTENANCE FOUND THE APU GEARBOX VENT LINE HAD EVIDENCE OF COKING AND CLEANED THE VENT LINE PER AMM 49-26-55. MAINTENANCE ALSO REPLACED THE APU GEARBOX AIR OIL SEPARATOR ADAPTER CARBON SEAL PER AMM 49-26-54 (AALA202406250245) A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.