From the 767 world, I assume that 757 is similar
The sequence in which you pressurize or remove pressure from the hydraulic systems can cause fluid to move between the center and right systems. This can cause a high fluid level in one system and a low fluid level in the other system. If you set the parking brake in one of these conditions:
- the right and center hydraulic systems pressurized
- only the right hydraulic system pressurized
- no hydraulic system pressurized
and then release the brake with only the center system pressurized, thefluid can move to the center system. If you set the parking brake withonly the center system pressurized and then release the brake in one ofthese conditions:
- the right and center hydraulic systems pressurized
- only the right hydraulic system pressurized
- no hydraulic system pressurized
the fluid can move to the right system. To keep the movement of thefluid between the systems to a minimum, pressurize the right systembefore you pressurize the center and left systems. Also, remove thepressure from the center and left systems before you remove the pressurefrom the right system.