What was found
ON FLIGHT 4307 THE CREW REPORTED THE COCKPIT SMELLED OF BURNING OIL. THE AIRCRAFT WAS REMOVED FROM SERVICE. COMPLIED WITH ETN EM-72-034R4 ENGINE ODOR EVENT TROUBLESHOOTING SUPPLEMENT WHICH VERIFIED ENGINE 1 AS ODOR SOURCE. SUBSEQUENTLY COMPLIED WITH R-R FIM 72-00-00-810-814 STEPS 01, 18, 06 ,07, 08, 09, 10 AND 24. REMOVED AND REPLACED THE LEFT HAND ENGINE IAW WC 71-000-00. THE OPERATIONAL AND LEAK CHECK WAS GOOD AT THIS TIME, NO OTHER DEFECTS NOTED. THE AIRCRAFT WAS RETURNED TO SERVICE.