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/

 

[D60]

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/

That thread suggests 30-35 psi is "unusually high" but I always start with my Branick at 30psi -- you just get a better flow. The only reason I don't go more is that I'm not sure how much positive pressure plastic reservoirs can withstand before they blow apart or pop off. @The Critic have you ever found the limits of a particular vehicle?

Beyond that is there anything special about Ford's software, or is it just doing the traditional cycling of the ABS module? @bdcardinal any idea?

 

[SureshR]

As f

Beyond that is there anything special about Ford's software, or is it just doing the traditional cycling of the ABS module? @bdcardinal any idea?

Nothing that i can think of beyond a steady and controlled pressure and cycling the abs module.

 

[bdcardinal]

That thread suggests 30-35 psi is "unusually high" but I always start with my Branick at 30psi -- you just get a better flow. The only reason I don't go more is that I'm not sure how much positive pressure plastic reservoirs can withstand before they blow apart or pop off. @The Critic have you ever found the limits of a particular vehicle?

Beyond that is there anything special about Ford's software, or is it just doing the traditional cycling of the ABS module? @bdcardinal any idea?

Could be the ABS cycling. Ford limits what I can look at for non North American vehicles.