I've got an '89 Bronco II. After letting it sit for about 2 months, I decided to drive it and my brake pedal went straight to the floor. The brakes didn't work at all. I've replaced the master cyl., bled the entire system. Found leaks in the wheel cylinders in the rear. Replaced them. Bled the system again. As long as the vehicle is off, I can get great pressure on my brake pedal, but as soon as I turn it on, it goes straight to the floor again. I'm stumped, anybody have any ideas?

thanks

 

your power brake booster is probably bad. Sometimes the diaphram inside the booster dries out and cracks causing it to suck/blow air. It's happened to me in the past.

 

Agreed, power brake booster.

 

You know, that is what I thought a couple of days ago, but I called 3 different parts stores and they all concurred that my booster couldn't possibly be causing my problem. I went and bought the booster today and put it in and guess what... I have brakes! Thanks guys!

 

glad to here you have brakes on your rig!!