B737 MAX Series Undifferentiated
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 75; Flight Crew Type 4000
Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Manuals; Procedure
Upon entering the aircraft; the brake accumulator pressure was 2;000 psi. The previous Crew reported no issues with the pressure. Turning the B electric pump on immediately brought the pressure back to 3;000 psi. When the pump was turned off; the pressure fell to 2;000 psi in a few seconds. I reported the issue to Maintenance who responded to the aircraft. While troubleshooting the issue; the AMT asked if the previous Crew had waited 10 seconds between turning the A and B electric hydraulic pumps off. The previous Crew had departed; so we were unable to determine the answer. When I asked why he wanted to know this; he responded that the Maintenance manual directs a ten second delay to make sure a shuttle valve has time to complete travel on MAX aircraft. Pilots do not have this guidance; and routinely turn both pumps off at the same time or in quick sequence as part of the shutdown flow. I've experienced low accumulator pressure on several MAX aircraft over the last few months resulting in flight delays; so I thought I should forward this concern.
B737 MAX First Officer reported the maintenance procedure to manage electric hydraulic pumps is not included in pilot manuals; resulting in non standard brake accumulator pressure variance.