Brake pedal hissing when pressed

[AVR2]

I'm getting a hissing sound when I press the brake pedal. Just in the last week, we've noticed that we need to put more pressure on the pedal about halfway through a stop. I guess this probably points to the brake booster?

I've tried the FSM test for the booster - engine off, pump the pedal until it's hard, hold pedal down, start the engine, check to see that the pedal drops down. It passes this test, but there's the hissing sound with the pedal pressed and the engine running.

I had a quick look just now for any obvious breaks in vacuum lines, but I couldn't find anything.

 

[Snail Farmer]

Sounds more like the master cylinder to me...

I guess I should elaborate a little more. I've seen that happen when the bolts that hold the master cylinder to the booster aren't tight. I would check to make sure they are first and foremost. If they're loose, tighten them, and bleed the brakes. If that's not it, then I would say bad booster.