As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REF LOG 5: DUE TO HISTORY OF OIL SMELL IN COCKPIT, REPLACE LEFT PACK PRIMARY AND SECONDARY HEAT EXCHANGERS PER TOMC. REPLACED BOTH PRIMARY & SECONDARY HEAT EXCHANGERS IN LEFT PACK IAW MM. NEED TO ACP LEFT PACK BURNOUT. REPLACED RT AND LT RECIRCULATION AIR FILTERS PER MM. PERFORMED ENGINE BURNOUT ON THE LEFT ENGINE NO SMELLS NOTED.