I have an '88 XJ and I am currently having brake problems that I believe are centered around my booster. When I bought the jeep, the brakes were very soft. I immediately replaced pads/rotors and shoes and installed a new MC. The problem then was the leaking vacuum sound coming from the booster. To remedy this I installed a booster from a '91 parts XJ I have. With this booster installed, the pedal continued to go to the floor and hiss (making the leaking vacuum sound) and would gradually stop the Jeep. Today, I pulled the booster from a '90 in the local pick-n-pull yard. Now my problem is that I have a very VERY stiff pedal, and a very loud hiss from the time the pedal begins to depress. To give you a reference of how hard the pedal is to depress, I am 6'3" and have my seat back all the way and have to brace myself against the seat to actually get the pedal depressed 1-2".
New MC, pads, rotors, shoes.
Original booster: vacuum leak, pedal to the floor.
Second booster: vacuum leak, pedal to the floor.
Third booster: VERY loud vacuum leak, impossibly stiff break pedal.
Has anyone out there had similar problems to this? I have looked at this thing numerous times and there I can't see any possible way that I could have installed this incorrectly, but I am open to any advice you are willing to send my way!