Hi i have lost brakes recently. I push the peddle and it bottoms out and then is harder to push, it does stop the truck but with a lot of pressure. I have been hearing a hissing coming from the driver side engine compartment for a month + so I am assuming I must have a vacuum leak in the system? To add to this, yesterday in traffic down a long downhill I shut the truck off 5 mins or so, for excessive idling and used the brakes pretty heavily down hill with the truck off. After this they seemed fine but then later that night began to bottom out and throw the brake light on the dash. Any ideas. It is a 1986 6.9 n/a with a live-in full size lance camper. It just snowed here in CO so I'd like to get this dialed before I move very far.