my break petal wont go down... 88 GMC S15 Jimmy?

[Bailey Kathleen]

88 GMC S15 Jimmy, 2WD 2.8l V6

About a week ago I started leaking brake fluid from where one of the lines connect to the brake master cylinder thingie.. I've been checking the level of fluid and topping it off once or twice a day since then, and have not had any sponginess with the petal, but the other day I started it up to go somewhere and when I hit the breaks the petal wouldn't go down at all, I had to shift into park while moving to get it to stop. I'm a bit confused because everything i've read says that leaking and air in the lines will make the petal just go to the floor. I would appreciate a bit of advice on this.. I am trying my best to learn to work on my truck myself and would rather not have to take it in anywhere.

 

[Molson02536]

88 GMC S15 Jimmy, 2WD 2.8l V6

About a week ago I started leaking brake fluid from where one of the lines connect to the brake master cylinder thingie.. I've been checking the level of fluid and topping it off once or twice a day since then, and have not had any sponginess with the petal, but the other day I started it up to go somewhere and when I hit the breaks the petal wouldn't go down at all, I had to shift into park while moving to get it to stop. I'm a bit confused because everything i've read says that leaking and air in the lines will make the petal just go to the floor. I would appreciate a bit of advice on this.. I am trying my best to learn to work on my truck myself and would rather not have to take it in anywhere.

Sounds like the BRAKE BOOSTER has failed.

Start the engine and stick your head under the dash as far as you can get in back of the brake pedal. If you can hear a hissing sound, Like a vacuum leak, This would most likely be a ruptured diaphram in the brake booster which is the large round black device mounted on the firewall in back of the master cylinder in the engine compartment.

You can also disconnect the big rubber vacuum line from the brake booster and put your thumb over the vacuum line and see if the engine runs smoother.

If you can hear the hissing noise per above and or the engine runs smoother putting your thumb over the big vacuum hose, Replace the brake booster.

Here is a link to your brake parts to your Jimmy.

http://www.compnine.com/index.php?u...delid=7016&capuid=1&majorgroup=04&grouptype=B

http://www.compnine.com/index.php?u...delid=7016&capuid=1&majorgroup=04&grouptype=B

http://www.compnine.com/index.php?u...delid=7016&capuid=1&majorgroup=04&grouptype=B