Narrative:

Ferry flight. During cruise flight at FL410; the left hydraulic edp low pressure light and the master caution light came on. A few seconds later; the right hydraulic edp low pressure light came on. We performed the QRH procedure and declared an emergency. The closest airport was ZZZ1; but the weather was not suitable for an approach. All airports were experiencing fog with low ceilings and visibility. We contacted dispatch for assistance with a suitable field. Dispatch recommended ZZZ which was showing 200 ft ceiling & 2 miles visibility. We landed safely without further incident.callback conversation with reporter revealed the following info: reporter stated that this individual aircraft had previous instances of this same failure. Although the left and right engine driven pumps (edp)'s had low pressure lights illuminate along with the master caution warning; the system 'a' or 'B' electric motor driven pumps (emdp)'s continued to function normally. The left and right engine driven hydraulic pumps and hydraulic filters were replaced; with engine runs and hydraulic filters changed again to verify no metal chips were found. Reporter stated he was informed by a lead mechanic of an airworthiness directive (ad); or service bulletin (sb) that removed the hydraulic reservoir pressurization module to address the engine pump failures on their pre nexgen B737-800.

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Original NASA ASRS Text

Title: A B737-800 crew diverts to a nearby airport when both engine drive hydraulic pumps indicate low pressure.

Narrative: Ferry Flight. During cruise flight at FL410; the LEFT HYD EDP low pressure light and the master caution light came on. A few seconds later; the RIGHT HYD EDP low pressure light came on. We performed the QRH procedure and declared an emergency. The closest airport was ZZZ1; but the weather was not suitable for an approach. All airports were experiencing fog with low ceilings and visibility. We contacted Dispatch for assistance with a suitable field. Dispatch recommended ZZZ which was showing 200 ft ceiling & 2 miles visibility. We landed safely without further incident.Callback conversation with reporter revealed the following info: Reporter stated that this individual aircraft had previous instances of this same failure. Although the left and right engine driven pumps (EDP)'s had low pressure lights illuminate along with the master caution warning; the System 'A' or 'B' electric motor driven pumps (EMDP)'s continued to function normally. The left and right engine driven hydraulic pumps and hydraulic filters were replaced; with engine runs and hydraulic filters changed again to verify no metal chips were found. Reporter stated he was informed by a Lead mechanic of an Airworthiness Directive (AD); or Service Bulletin (SB) that removed the Hydraulic Reservoir Pressurization Module to address the engine pump failures on their pre NexGen B737-800.

Data retrieved from NASA's ASRS site as of May 2009 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.