Brake master cylinder / booster issue

[SureshR]

So I have a Ford Endeavour (aka Ranger with a SUV body, as sold in Australia / Asia / South Africa), and it had what looked like a classic booster failure. Brakes lost vacuum a bit, and then went hard. After removing and inspecting the master cylinder and booster, Ford told me that the master cylinder was fine, but the booster had failed - and they've replaced it.

Braking was ok for the first day but is starting to turn spongy again, over the weekend. Headed back to Ford on Monday, but does this look like the MC has failed or is it intact? The brake fluid stains, Ford says, are from a spill when disconnecting the brake lines, and the spindle in the middle looks clean which seems to indicate that the MC's seal hasn't failed as such.

 

[Lubener]

That's some sloppy work and they didn't clean up the spill.. Since the back of the master cylinder is not corroded, I don't think the fluid is leaking out the rear of the m/c. I would start with bleeding the brakes again. since they admitted to disconnecting the lines and air still could be in the system. If they bled the system the old fashioned way, pressing the pedal down to the floor while bleeding can damage the seals in the master cylinder and cause it to bypass fluid.

 

[SureshR]

That is what I suspect as well, there’s a specific brake bleeding procedure in Ford with the Ford laptop connected to the OBD

https://www.f150gen14.com/forum/threads/brake-fluid-pressure-bleeding.19067/