Narrative:

After pushback from gate 'X' to operate a flight overwater on a B737-700; I started number one (left) engine per normal procedures. Approximately 10-20 seconds after engine stabilized; the oil filter bypass caution light illuminated on the upper display unit. Captain requested that I perform the QRH (quick reference handbook) checklist for the oil filter bypass light. The QRH directed the flight crew to perform the engine failure/shutdown checklist; as the light was illuminated at idle power. I shut the engine down and requested a tow back to the gate. Maintenance crew came to the aircraft and inspected oil filter and chip detectors. The maintenance crew reinstalled the components and a mechanic again started the # 1 engine at the gate. The oil filter bypass caution light again illuminated. Eventually; the maintenance crew deferred the oil filter bypass warning system per MEL 79-2. The corrective action entered by maintenance in the aircraft logbook read very vaguely and only indicated the deferral per MEL 79-2. No placard sticker was placed near the affected indicator by the maintenance crew involved with this event; as required by the MEL/cdl manual. Captain and I studied and discussed the MEL verbiage very carefully. The MEL specifically stated that maintenance must determine the cause of the system (oil filter bypass light) malfunction. No cause of the malfunction was ever revealed to captain nor myself by the maintenance crew. It was not entered as corrective action in the logbook either. The MEL does not contain an (M) maintenance item to disable the system. As such; the light/system was not disabled. The MEL does not contain an (O) operation item directing the flight crew to ignore the light and/or take any action regarding the malfunctioning system. We were obligated to follow the QRH and ultimately shut the engine down [if in-flight] had the oil filter bypass light illuminated again under the circumstances at the time. Captain and I agreed that we had no relief provided by the MEL or any other source other than a verbal instruction from the assistant chief pilot to just ignore the light if it comes on. A customer service duty manager arranged for another aircraft; to which we transferred to and completed the flight safely to ZZZ1. (Yes; a bit late; but safely). I believe that the deferral; MEL 79-2 was incorrectly applied to this malfunction. It became obvious to me that delay mitigation; not safety; was the pressing concern at the time. MEL 79-2 does not provide any relief to the flight crew to ignore the [bypass] light and thus to not perform the applicable QRH checklists. The maintenance crew involved did not provide any determination; at least to the flight crew or in the aircraft logbook; as to the cause of the system malfunction. Furthermore; a verbal instruction from the assistant chief pilot to ignore the caution light if it comes on does not provide any legal relief to the flight crew. In a hypothetical point-of-view of an FAA safety inspector; I believe this would have been a 'major' problem as it was handled by maintenance and dispatch. Fortunately; captain and I were provided with another aircraft which was determined to be safe and airworthy; without asserting a 'refusal' of the B737-700.

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Original NASA ASRS Text

Title: A First Officer reports he believes that departure delay mitigation and not safety; was the pressing concern when Maintenance improperly deferred a # 1 engine Oil Bypass Light illumination under MEL 79-2 on their B737-700. Lack of Maintenance entry in Logbook regarding the troubleshooting; failure to placard light and lack of MEL relief contributed to pilots concerns.

Narrative: After pushback from Gate 'X' to operate a flight overwater on a B737-700; I started number one (left) engine per normal procedures. Approximately 10-20 seconds after engine stabilized; the Oil Filter Bypass Caution Light illuminated on the Upper Display Unit. Captain requested that I perform the QRH (Quick Reference Handbook) checklist for the Oil Filter Bypass light. The QRH directed the flight crew to perform the Engine Failure/Shutdown checklist; as the light was illuminated at idle power. I shut the engine down and requested a tow back to the gate. Maintenance crew came to the aircraft and inspected oil filter and chip detectors. The maintenance crew reinstalled the components and a Mechanic again started the # 1 engine at the gate. The Oil Filter Bypass Caution light again illuminated. Eventually; the maintenance crew deferred the Oil Filter Bypass Warning System per MEL 79-2. The corrective action entered by Maintenance in the Aircraft Logbook read very vaguely and only indicated the deferral per MEL 79-2. No placard sticker was placed near the affected indicator by the maintenance crew involved with this event; as required by the MEL/CDL Manual. Captain and I studied and discussed the MEL verbiage very carefully. The MEL specifically stated that Maintenance must determine the cause of the system (Oil Filter Bypass light) malfunction. No cause of the malfunction was ever revealed to Captain nor myself by the maintenance crew. It was not entered as corrective action in the logbook either. The MEL DOES NOT contain an (M) Maintenance Item to disable the system. As such; the light/system was not disabled. The MEL DOES NOT contain an (O) Operation item directing the flight crew to ignore the light and/or take any action regarding the malfunctioning system. We were obligated to follow the QRH and ultimately shut the engine down [if in-flight] had the OIL FILTER BYPASS light illuminated again under the circumstances at the time. Captain and I agreed that we had no relief provided by the MEL or any other source other than a verbal instruction from the Assistant Chief Pilot to just ignore the light if it comes on. A Customer Service Duty Manager arranged for another aircraft; to which we transferred to and completed the flight safely to ZZZ1. (Yes; a bit late; but SAFELY). I believe that the deferral; MEL 79-2 was incorrectly applied to this malfunction. It became obvious to me that delay mitigation; not SAFETY; was the pressing concern at the time. MEL 79-2 does not provide any relief to the flight crew to ignore the [Bypass] light and thus to NOT perform the applicable QRH checklists. The maintenance crew involved did not provide any determination; at least to the flight crew or in the aircraft Logbook; as to the cause of the system malfunction. Furthermore; a VERBAL instruction from the Assistant Chief Pilot to ignore the caution light if it comes on does not provide any legal relief to the flight crew. In a hypothetical point-of-view of an FAA Safety Inspector; I believe this would have been a 'major' problem as it was handled by Maintenance and Dispatch. Fortunately; Captain and I were provided with another aircraft which was determined to be safe and airworthy; without asserting a 'refusal' of the B737-700.

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.