As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DETECTED A MILD TRANSIENT ODOR ON DESCENT THROUGH FL 200 MOMENTARILY THEN AGAIN AT 12000 FT, TURNED OFF LEFT BLEED AND ODOR DISSIPATED ODOR WAS SWEATY SOCK. MAINTENANCE FOUND OIL BEHIND LEFT ENGINE SPINNER. REMOVED AND REPLACED LEFT ENGINE. ALSO REPLACED LEFT OZONE CONVERTER DUAL HEAT EXCHANGER CONDENSER/REHEATER AIR CYCLE MACHINE AND FLT DECK MUFFLERS. ACCOMPLISHED ENGINE RUNS AND PACK BURN. ALL CHECKS NORMAL.