F-150 brakes solid when engine off, but go to the floor when on.
2014 Ford F-150. Part of master cylinder recall. Have replaced the master
cylinder 2X. Checked the Power booster, not an issue. Checked the ABS
modulator, it is fine. When I push the brake with engine off, very solid. I'm not
losing brake fluid. When I turn the engine on, the pedal sinks to the floor, and I
have no brakes. What do I check?