What was found
EXTREME SMOKE IN CABIN WHEN AIR IS ON. COULD NOT DUPLICATE PILOT DISCREPANCY. PERFORMED BORESCOPE OF APU INLET & NOTED SOME COKING ON STATOR BLADE BETWEEN THE 4 & 8 O'CLOCK POSITION. SERVICED APU WITH .9 QTS OF BP2380 ENG OIL. PERFORMED 1.5 HOUR APU RUNS WITH BLEED AIR IN AUTO, MAN & HOT & COLD. PERFORMED SECOND BORESCOPE OF APU INLET, NO OIL DETECTED. CHECKED POST RUN APU OIL LEVEL & NOTED ZERO CONSUMPTION. POWERED UP CABIN & GALLEY SYSTEMS FOR 5 HOURS WHILE PERFORMING OTHER MX, NO SMOKE NOTED. INSPECTED APU LOAD CNTRL VLV FOR OIL RESIDUE, NO DISCREPANCY NOTED. CLEANED COALESCE SOCKS LAW 21-01-12 & REINSTALLED. OPERATIONS & LEEK CHECKED GOOD. PERFORMED LT & RT ENGINE RUNS WITH WING & ENGINE COWL ANTI-ICE SELECTED & CHECKED FOR CABIN SMOKE, NO DISCREPANCY NOTED.