1995 Jimmy Power Brake Problems

[baybum]

1995 GMC Jimmy 4x4 4dr v6 4.3

My power brakes just stopped working this morning on the way to work. Noticed some kind of liquid on carpet to the right of the gas pedal. Also noticed I have had to give the truck gas to start since one day last week. I haven't seen any leaks on the inside of any wheels or master cylinder. I'd rather not throw un-needed parts at it. When applying the brake pedal I hear a constant hiss at the pedal until I let go of the brake. Anyway to narrow down to vacuum leak, master cylinder failure, or power booster failure?

[old_master]

Power brakes use engine vacuum for assist. Pinch off the vacuum line between the engine and the booster with vise grips and see if the noise quits, and if the engine runs better. If so, you'll need a new booster. The liquid might be brake fluid, if so, the master cylinder is leaking and will need to be replaced as well. (two separate problems)

[baybum]

Thanks for the help. It was the brake booster, and the engine feels better now also. The liquid turned out to be the rear washer fluid coming from the disconnected hose coming in through the firewall.