OK, I have a 92 cherokee with non-abs brake system. Out of the blue the brake pedal went down and applied the brakes but wouldn't come back up unless i stuck my toe under it and pulled it back up.
Things i already tried:
Replaced Master cylinder and vacuum booster.
Completely replaced rear brake system.
Made sure i actually had vacuum to the booster.

Never had this happen before and any ideas would be greatly appreciated.

 

Did you look under the dash to see if you have a brake pedal return spring that might have sprung?

(I don't know and I'm away from my service manuals, just spitballing here.)

 

yep, first thing i checked. the 92 cherokee doesn't have a return spring. I am going to try and bleed the system again and see if that helps.

update: when i disconnect the vacuum hose from booster, the brake pedal kind of works right, just feels if there is still a lot of air in lines. Plug hose back in and pedal goes to floor and moves up and down when I rev motor.

Do i need an exorcist?

 

Could be the check valve at the booster.

 

Huge lesson learned: yes it was a bad VB, when you pay out a HUGE amount of money for a rebuilt VB, make sure you install it correctly!!!!!!
At the pedal end, the rod is curved at the end. THAT CURVE GOES DOWN!!!!!!

If you install it with the curve up, as soon as you push the pedal it it breaks and you are stuck with an expensive door stop.

 

Well you finally got er done anyhow!
Thanks for the update!

 

Was going to suggest the booster, but you beat me to it - good call!