What was found
5/10/2009 AT APPROXIMATELY 1:00 AM, ACFT WAS CLIMBING OUT OF BFI. THE FLIGHT CREW EXPERIENCE A LT ENGINE LOW OIL LIGHT. THEY COMPLIED WITH A PRECAUTIONARY LT ENGINE SHUTDOWN AND RETURNED TO BFI WITHOUT FURTHER PROBLEMS. MX WAS CONTACTED TO CORRECT THE PROBLEM AND THEY DISCOVERED THE LT OIL DIPSTICK DID NOT HAVE A O-RING ON IT. THEY INSTALLED A O-RING AND CLEANED AND LEAK CHECKED THE ENGINE WITH GOOD RESULTS. THE ACFT WAS RETURNED TO SERVICE. THE FLIGHT CREW HAD CHECKED THE OIL BEFORE DEPARTING BFI AND SUSPECT THE O-RING WAS LOST AT THAT TIME.