These symptoms are typically caused by a failing brake power booster unit, likely a vacuum
valve in the booster unit.
Not exact matches
The next attempt,
in April, a stuck
valve prevented the
booster from reacting fast enough to maintain position after a successful touchdown.
You said you replaced the line, but there is a check
valve in the line, it is probably installed at the
booster end of the line.
The hissing sound you heard was air leaking through either a vacuum or vent
valve in the brake
booster itself.
Assisted
in the repairs of main feed pumps,
booster pumps, steam
valves, fuel pumps, and pressure regulators.