So of coarse another issue. 01 Cherokee. I get in to move it today and the brake pedal travels half or 3/4 to the floor before the brakes apply. It will still lock the brakes up. No leaks and pads and shoes good. Just adjusted the rears last week. If I press the pedal while it’s off I get good pressure for about 1&1/2 pumps then it’s the same.

The back story is about 5 years ago when we first drove it the booster wasn’t quite working because it sat for a bit. But then was fine by the end of the drive. Over the years some days there was an audible hiss from the booster. Always planned on changing it but never did.

From researching it sounds like it’s a bad master cylinder but I’m not quite convinced. I do have a 98 that I could pull either part from if they’re compatible. Just given the past issue with the booster I would have thought it was the problem. Any help is much appreciated.

Ok. Thanks man. At least a master cylinder is only $50. I just put the Jeep up for sale anyway so I’m not sure if I’ll bother changing it. My wife was just telling me the other day about how she had to lock up the brakes to avoid some *** that pulled out in front of her. I bet that’s when it happened. I had just adjusted the rear brakes the day before that too. She’s currently driving the 98 I just put on the road instead.

Just for giggles, see if her panic stop knocked one of the rear drum shoes out of place. Here’s the background - I had done some work on my rear drums and some time later my brake pedal got mushy. I spent weeks bleeding brakes and messing around with the front discs, even replaced the master cylinder. Nothing worked, I still had mushy brakes, the pedal would go to the floor and I’d only have partial stopping power.

Out of ideas, I pulled off the rear drums. On one side I found the rear shoe on top of the drum brake guts, over the hydraulic actuator. The metal part of the shoe was still in place, but the (ceramic? graphite?) wear part had separated and rotated over the top until it became lodged.

I put in a new shoe and my brake system worked like new again. What was happening was, when I pressed the brake pedal all the pressure was going to the right rear drum since there was no shoe there to push back. Without any material there it wasn’t able to self-adjust either.

Anyway, if all the regular ideas don’t work, maybe have a look.