Narrative:

Performed the engine run checks. Samples of oil from both engines were taken; as were both engine oil filters were changed. During this procedure it is required to change the o-ring around the oil filter cap housing. This was performed in accordance with the computerized aircraft maintenance program (camp) card. Both engine oil filter caps were safety wired. Both engines were run up to 70% N1 for a leak check; no leaks were found at this time. Two days later; the sabreliner 65 departed for a flight. Within fifteen to twenty minutes; the aircraft had returned with the number one engine shut down. During the post flight briefing the flight crew informed me they had shut the number one engine down as per the emergency procedure manual. The crew said they had got the master caution light as well as the low oil pressure light for the number one engine.upon inspection of the engine cowling; oil was everywhere. I opened the engine cowling; oil was everywhere as well. I noticed the oil drip from the oil filter cap. I removed the oil filter cap; the o-ring that was installed [two days earlier] was broken in half. The o-ring was replaced; oil was brought back up to the normal operating range; as it was before the flight that morning. Four quarts of oil was all that was lost during the flight. The engine was leaked checked; and brought up to 85% N1; no leak was detected. Three phone calls were made to insure that the engine had not been damaged; one to sabreliner; one to the engine repair provider and the last to the engine insurance carrier. All three said that they felt strong that there was no damage to the engine as the result of losing only four quarts of oil. No further evidence of an oil leak has been found at this time. A second engine run was performed. Lighting was a factor during the described events in the first paragraph; though not problematic. The light issue has since been since resolved. Additional procedures have been put into our standard operation procedure (SOP) for leak checking.

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Original NASA ASRS Text

Title: A cut oil filter cap O-ring was found to be the cause of a return to land by a Sabreliner 65 that had a Master Caution; Low Oil Pressure indication.

Narrative: Performed the Engine Run Checks. Samples of oil from both engines were taken; as were both engine oil filters were changed. During this procedure it is required to change the O-ring around the oil filter cap housing. This was performed in accordance with the Computerized Aircraft Maintenance Program (CAMP) Card. Both engine oil filter caps were safety wired. Both engines were run up to 70% N1 for a leak check; no leaks were found at this time. Two days later; the Sabreliner 65 departed for a flight. Within fifteen to twenty minutes; the aircraft had returned with the number one engine shut down. During the post flight briefing the flight crew informed me they had shut the number one engine down as per the Emergency Procedure Manual. The crew said they had got the Master Caution light as well as the Low Oil Pressure light for the number one engine.Upon Inspection of the engine cowling; oil was everywhere. I opened the engine cowling; oil was everywhere as well. I noticed the oil drip from the oil filter cap. I removed the oil filter cap; the O-ring that was installed [two days earlier] was broken in half. The O-ring was replaced; oil was brought back up to the normal operating range; as it was before the flight that morning. Four quarts of oil was all that was lost during the flight. The engine was leaked checked; and brought up to 85% N1; no leak was detected. Three phone calls were made to insure that the engine had not been damaged; one to Sabreliner; one to the engine repair provider and the last to the engine insurance carrier. All Three said that they felt strong that there was no damage to the engine as the result of losing only four quarts of oil. No further evidence of an oil leak has been found at this time. A second engine run was performed. Lighting was a factor during the described events in the first paragraph; though not problematic. The light issue has since been since resolved. Additional procedures have been put into our Standard Operation Procedure (SOP) for leak checking.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.