Brakes disappear when engine running and MBC

Hi,

I lost my brakes just driving around town

When the engine is off the brake pedal is hard. When the engine is running I have to pump the brakes a couple of times to get any braking. Is it the MBC at fault?

My Puma has later model 256mm front brakes and rear Mondeo 258mm discs; no ABS; earlier model (black) MBC; Pads and discs are healthy; braided brake hoses; Brake fluid changed less then a year ago with MBC "bench bleed"; Felt no air in the system before the abrupt brake loss.

And one more thing. After completing the bigger disc package modification, the brake pedal travel increased, the brakes seem to have little bite. If it's the MBC at fault, maybe I should change to a 25.4mm bore MBC from a MONDEO Mk II 09/1996 - 11/2000?

Check your disk thickness, also your wheel bearing nuts, if lose they can increase brake travel. As for swooping master cylinder the FRP uses the same master cylinder as the standard puma and works fine with rear disks and larger disks and alcons on the front.
If disks and wheel bearing are ok, I would say you have a problem with the rear disk conversion, possably disk and calaper alignment. One way of proving this would be to clamp both hoses at the back and see if theses an improvement.

the discs thickness is fine , bearings are ok. Also this wouldn't cause all of a sudden to go from having brakes - to not having them at all and pedal to the floor.

It sounds like an issue with the servo to me

definitely sounds like the brake booster to me as well that, possible vacuum leak?... ill assume you've check for leaks?? but its possible or maybe the master cylinder has giving up or flipped a seal maybe?