diagnose a leaking vacuum booster. pump the pedal about 4-5 times until it gets high and tight. start the engine with foot firmly on the brake pedal. If the pedal sinks when the engine starts, the booster is probably good. To check for a master cyl leak, remove the two flange nuts(NOT THE LINES) holding the m/c to the booster. Pull the m/c away from the booster and look or feel for any wetness. Any wetness indicates a fluid leak and the m/c NEEDS replaced. Also, brake fluid from a leaking m/c will get sucked into the booster and eat away at the rubber diaphragm inside, shortening it's life.

 

Hi, don't know if you're still following this forum. You probably don't have your gen 1 ody anymore. If you are listening, I am wondering what your fix to this problem was. I am experiencing this very issue on my 96. When I push my brakes I hear a sound which is like someone breathing our really hard, like air leaking from the booster. The sound is actually coming from inside the cabin. Also, my power brakes don't work anymore, so I have to push really hard on the brake pedal. It is like I have pre-power brakes brakes. Any help would be appreciated. I may take the other person's advice to open it up. I do not think it is the MC, as my brakes don't go down to the floor. Thanks everyone!

 

Sounds like you need to replace the booster. It's basically a rubber diaphragm using engine vacuum to help push the pedal rod along.