What was found
JUST BEFORE LANDING AN ACRID SMELL WAS NOTICED IN THE AIRCRAFT. THE FLIGHT ATTENDANTS REPORTED THE RT AFT LAVATORY SMOKE DETECTOR WAS SOUNDING. NO VISIBLE SMOKE WAS SEEN AND NO FIRE WAS LOCATED. IT WAS NOTED THAT THE APU WAS NOT OPERATING. AIRCRAFT LANDED NORMALLY AND TAXIED TO THE GATE WITHOUT INCIDENT. MAINTENANCE DID NOT FIND A SOURCE FOR THE FUMES BUT REPORTED THE RT SEPARATOR SOCK AS (CONTAMINATED). NO LEAKS OF ANY TYPE (FLUID OR AIR) COULD BE FOUND. COMPLIED WITH BURNOUT PROCEDURES, REPLACED THE RT COALESCER BAG, AND RETURNED THE AIRCRAFT TO SERVICE.