funny brake noise HELP

my brakes started making a hissing sound when i press them down.dont realy have a clue what it could be. thanks for any help.

Leaking booster comes to mind -- although I don't know how you would check exactly what's happening. Someone else needs to chime in.

the sound comes from the floor board and my brake light hasnt come on yet if that helps

I had that problem on my 90. Hissed in real cold weather, once the engine warmed up, hissing went away. Never seemed to affect braking performance.
Still sounds like the booster to me.

Leaking diaphragm in brake booster.

how would i check to make sure not to doubt or any thing just wanna make sure.

Diaphragm is internal to booster --- don't know if there is really any way to positively check without taking the thing apart. However I see there seems to be a core charge on them, so you might not want to mess with it.

Hey Sniper - I've got the exact same problem going on right now myself - been reading the posts all day, and became convinced that I had to replace the Booster (about $130 plus the time to bleed all the lines, etc)... Then I found out about the Brake Booster Vacuum CHECK VALVE. This is a $10 piece of plastic elbow/adapter on the front of the booster that the vacuum hose connects to - and I'm being told by other posters that if it's bad it COULD be causing all the same problems/symptoms that would be happening if the entire booster went bad. check my profile for a link to the thread i'm discussing that in, and/or search the tech formus for keyword "brake booster". TONS of kickass info on this site!
Daryl