Went to a local lake today to check the ice, set the parking brake on the ramp, got out, checked the ice, came back and the brakes were hard as a rock, and there is a constant hissing sound coming from the firewall when the brakes are applied. I know my pads are pretty much gone upfront and I was going to replace them tommorow. what could it be? Is a vaccum leak likely, and if so, where do the lines run, and where can I find vaccum line?
also appeared as if my brake fluid was low, so I put more in it, but it made no difference.

 

Vacuum leak, or failed brake booster. Line runs from the intake manifold, to the brake booster. Start at the booster, and follow it back. See what ya got.

 

alright, sounds good. I'll check it out