Brakes are really soft all of a sudden.

[T-ROD]

Yesterday my brake pedal went almost all the way to the floor. It stops fine at low speeds but the brake travels way to far and it stops like Im trying to stop 20k lbs. without trailer breaks. Also there is a clunk coming from somewhwere near the rear. The clunk only happens randomly so I really cant say it does it during certain types of braking just when I brake it will do it and sometimes it wont. Im looking at the master cylinder for the brake travel, any other ideas? Thanks

[WSStucker]

Same problem here, but without the clunk.

[WSStucker]

Bump..

[melmount]

subscribed, I had an excursion that did this. I never found out what it was. I replaced the master cylinder

[T-ROD]

Replaced the master cylinder as well. still having a similiar issue. A buddy thought it might be the abs valve/motor. Do obs trucks even have abs?

[WSStucker]

Bump again..

[T-ROD]

Now i have replaced the booster as well. Still the same issue. Bled all the lines including the abs valve. No difference. I found out that our trucks do have RABS (rear anti-lock brake system) retarded idea from ford, but anyways. Going to pull the rear brakes off tommorrow and see if there is something wrong back there since the rear brakes control pedal height. If everything is good back there Ill be replacing the abs valve.

[rolsmojave3]

Sounds like you lost something in the rear, weather it be a shoe seperating or wheel cyl blow out. I'd defenetly check it out prior to driving it.

[T-ROD]

Ok so I have replaced the master cylinder twice now because Napa has been having some issues with their master cylinders bypassing internally. I just replaced the ABS valve, bled all the lines, tightned up the rear brakes, replaced the parking brake cables because they were siezing up on me a little and I still have the same pedal creep. The brakes feel stronger but they will still slowly creep to the floor if I stand on them. Im at a loss now because I have replaced everything that could be causing the issue and I'm still having it. Im going to plug the holes on the master cylinder this weekend so I can isolate the master cylinder and see if my pedal still creeps if it does then I will have found my issue but if it doesn't I don't know what to do. Any suggestions?

[rolsmojave3]

Did you pull the drums to check it out?