What was found
ACRID-ONLY SMOKE SMELL IN COCKPIT AND CABIN NO SMOKE VISIBLE. OUT OF FL204 IN DESCENT BETTER BY 104. *S/D* REPLACED NR 1 ENGINE. SHOP INVESTIGATION REVEALED NO VISIBLE OIL IN THE ENGINE GAS PATH OR PNEUMATIC DUCTS AND NO EXTERNAL OIL LEAKS. NO OIL IN FAN HUB OR SPINNER. VACUUM TEST OF NR 1, 1.5 & 2 BEARING COMPARTMENTS INDICATED LEAKAGE ONE PPH OVER LIMIT. DISASSEMBLY REVEALED LIGHT OIL COATING ON INNER WALL OF LPC DRUM. COMPONENT TEST OF NR 1.5 & 2 BEARING CARBON SEAL ASSEMBLY REVEALED HIGH AIR LEAKAGE AT THE 1.5 CARBON SEAL OF 7.3 CU. FT. / MINUTE (LIMIT = 3.0 CU FT / MIN). POSSIBLE CAUSE OF COCKPIT AND CABIN ODOR IS OIL LEAKAGE PAST THE NR 1.5 CARBON SEAL.