B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors
While at the gate; Maintenance was working on the hydraulic system to defer the auto brakes and anti skid. They had told us not to turn on the electric hydraulic pumps or packs. Eventually we received a new [maintenance release] over ACARS saying they were done with the maintenance procedure and releasing the flight. We then prepared the aircraft for pushback which included turning the hydraulic pumps and packs on. As we were doing the checklist a mechanic began waving his arms and shouting outside my window to turn the packs off which I did. I requested a maintenance supervisor report to the cockpit and learned that the MRD should not have been issued and that they were still working on the hydraulic system. There were no injuries.
While working an auto brake inop condition; Maintenance released the plane to us via [electronic message]. This resulted in prematurely running the PREFLIGHT and BEFORE PUSH CHECKLISTS with the right hydraulic system open. We lost about a gallon on fluid before the [mechanic] got our attention by screaming up from the ramp to 'turn off the packs.'
B737NG flight crew reported they prematurely began to prepare for departure; including turning on packs and hydraulic pumps; after they were erroneously notified via ACARS that maintenance had completed their work.