I have recently had my 5.0 rebuilt. While I was waiting on the engine builder, I replaced the complete suspension and 90% of the brakes system. all new rotors, calipers, vacuum booster, mater cylinder some of the steel lines and all the rubber lines. Bleed all the air out and I could not stop a baby carriage with this brake system. I been doing brakes sense I was 18, never had this happen before. HELP
  • Sponsors (?)

Did you bench bleed the master cylinder, and are you sure it worked right?
My first two suspects are a bad MC and air bubbles that escaped your bleeding of the system. It would be easy if the vacuum line was not connected to the booster.
Are your brakes spongy, sinking to the floor, not pumping up, not getting power assist from the booster? Some more details about what you're experiencing would help pinpoint.

Assuming you have ABS? If (as mentioned by 7991LXnSHO) you didn't bench-bleed properly or got a bunch of air into the lines (with all that you changed that is very likely), the ABS may need to be bled. You can try the dirt-road lock-up trick (hit the brakes hard on a dirt road to get the ABS to actuate, do this a few times, and then bleed again) if you think that may have happened.

Another possibility is that the rod in the booster that pushes on the master cylinder wasn't adjusted properly. If the booster was 'rebuilt' that is very possible.
  • Useful
Reactions: 1 user