Narrative:

Situation: hydraulic B system engine driven pump low pressure light illuminated. Pressure gauge indicating normal. First officer flying. Approximately 250 NM from ZZZ. Actions: as the PNF, I read the QRH and followed the procedures (shut off the pump). I also mentioned that some time ago I'd read something about this happening on the long haul flts with the -700 and it had something to do with a sensor getting real cold and sending an erroneous signal. With that in mind, we asked ATC for a lower altitude. In the meantime, as I prepared so I could contact dispatch and maintenance, the first officer mentioned maybe we ought to ask for direct ZZZ. We requested expeditious routing to ZZZ and center accommodated us and further asked us if we were declaring an emergency to which we responded 'no.' (after that, every controller asked, 'are you declaring an emergency?' to which we consistently answered 'no.') as I was setting up the observer panel to use the phone, the first officer took the #1 radio (ATC) and told them negative, no emergency, soon thereafter, the hydraulic a system engine driven pump low pressure light also illuminated. I ran the QRH checklist once more. In the meantime, ATC queried us as to what kind of problem were we having. I responded by telling them that we were sorting it out (which was indeed the truth). I then conferred with dispatch and maintenance and planned to proceed to our destination, ZZZ (a maintenance base). We continued to ZZZ with a feeling that the situation was most likely altitude/temperature/duration of flight related, as advertised in that literature mentioned earlier. All the while, the a and B system hydraulic pressure gauges had not wavered with pressure indicating normal. However, since we had the time, I did review with the first officer what flight controls were affected with the loss of either a or B entirely and left the QRH open to the 'manual reversion' page (loss of both system). When another controller asked us what our problem was, I was then able to tell him it was a hydraulic system indication, but that we were planning a normal approach and landing at ZZZ.

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Original NASA ASRS Text

Title: B737 AT FL370 EXPERIENCED HYD PROB, REQUESTED LOWER ALT AND DIRECT ROUTING PROMPTING NUMEROUS ATC QUESTIONS.

Narrative: SIT: HYD B SYS ENG DRIVEN PUMP LOW PRESSURE LIGHT ILLUMINATED. PRESSURE GAUGE INDICATING NORMAL. FO FLYING. APPROX 250 NM FROM ZZZ. ACTIONS: AS THE PNF, I READ THE QRH AND FOLLOWED THE PROCS (SHUT OFF THE PUMP). I ALSO MENTIONED THAT SOME TIME AGO I'D READ SOMETHING ABOUT THIS HAPPENING ON THE LONG HAUL FLTS WITH THE -700 AND IT HAD SOMETHING TO DO WITH A SENSOR GETTING REAL COLD AND SENDING AN ERRONEOUS SIGNAL. WITH THAT IN MIND, WE ASKED ATC FOR A LOWER ALT. IN THE MEANTIME, AS I PREPARED SO I COULD CONTACT DISPATCH AND MAINT, THE FO MENTIONED MAYBE WE OUGHT TO ASK FOR DIRECT ZZZ. WE REQUESTED EXPEDITIOUS ROUTING TO ZZZ AND CTR ACCOMMODATED US AND FURTHER ASKED US IF WE WERE DECLARING AN EMER TO WHICH WE RESPONDED 'NO.' (AFTER THAT, EVERY CTLR ASKED, 'ARE YOU DECLARING AN EMER?' TO WHICH WE CONSISTENTLY ANSWERED 'NO.') AS I WAS SETTING UP THE OBSERVER PANEL TO USE THE PHONE, THE FO TOOK THE #1 RADIO (ATC) AND TOLD THEM NEGATIVE, NO EMER, SOON THEREAFTER, THE HYD A SYS ENG DRIVEN PUMP LOW PRESSURE LIGHT ALSO ILLUMINATED. I RAN THE QRH CHKLIST ONCE MORE. IN THE MEANTIME, ATC QUERIED US AS TO WHAT KIND OF PROB WERE WE HAVING. I RESPONDED BY TELLING THEM THAT WE WERE SORTING IT OUT (WHICH WAS INDEED THE TRUTH). I THEN CONFERRED WITH DISPATCH AND MAINT AND PLANNED TO PROCEED TO OUR DEST, ZZZ (A MAINT BASE). WE CONTINUED TO ZZZ WITH A FEELING THAT THE SIT WAS MOST LIKELY ALT/TEMP/DURATION OF FLT RELATED, AS ADVERTISED IN THAT LITERATURE MENTIONED EARLIER. ALL THE WHILE, THE A AND B SYS HYD PRESSURE GAUGES HAD NOT WAVERED WITH PRESSURE INDICATING NORMAL. HOWEVER, SINCE WE HAD THE TIME, I DID REVIEW WITH THE FO WHAT FLT CTLS WERE AFFECTED WITH THE LOSS OF EITHER A OR B ENTIRELY AND LEFT THE QRH OPEN TO THE 'MANUAL REVERSION' PAGE (LOSS OF BOTH SYS). WHEN ANOTHER CTLR ASKED US WHAT OUR PROB WAS, I WAS THEN ABLE TO TELL HIM IT WAS A HYD SYS INDICATION, BUT THAT WE WERE PLANNING A NORMAL APCH AND LNDG AT ZZZ.

Data retrieved from NASA's ASRS site as of July 2007 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.