2015 Ford Transit Connect - No brakes

while driving for a few hours on the freeway, the van starts to shake and speed drops from 65 to 45. when you put the brake on, it shakes more. left the freeway and minutes later the brake pedal hits bottom. had to pump the brakes until it grabbed againi.
a week later same situation exactly.
Sawgrass Ford could not find where the problem is.
when drivi9ng the car another 18 miles on side streets to be safe, the brakes went out again. again i had to pump the brakes till they worked. no idiot lights, no warnings

Most of the time that means the master cylinder is bypassing, BUT not always… Are you getting feed back from the brake pedal when you are braking??
Next is it is also possible (rare but I have seen it multiple times) that you have a loose wheel bearing(s)… The rotor can lean compressing the piston back into the caliper causing you to have to pump the brakes… But until you can test it while it is acting up that maybe a hard one… Lots of parts in the braking system that can go bad, ABS modules, Booster, Master cylinder, calipers, hoses/lines etc… But it rarely doing it, going to be hard to diag…

There are some pretty good (and smart) members that will hopefully have some more and better ideas…

A recent puzzler on the Best of Cartalk podcast, brake pedal would go to floor, mostly noticed after long freeway drive. Brake shops investigate, can’t figure it out, & give up. A few weeks later car’s brake lights fail, brake light switch under pedal replaced. Upon car’s return, owner asks: “Hey! How did you solve the pedal-goes-to-floor problem?” Shop says they only replaced brake light switch, didn’t work on the other problem. Turns out the old switch was pushing slightly on the brake pedal all the time, causing brakes to overheat on long high speed drives, boiling brake fluid, causing pedal to go to floor. New switch didn’t push on pedal.

Ask your shop to test if the brakes are getting unusually hot after longish freeway drive with little braking otherwise.

BTW, while I think very highly of the service department at my dealership, your vehicle is past warranty therefore try an independent shop, not a chain.

Because everything is computer or electronically controlled on the TC, you’ll need to clean the battery terminals first. This will reset the system and I mean removing the positive cable end as well as the negative cable end. Check the pads to see if there’s any life left to them. Then you’re going to have to have the line blead.

Looks like the OP was a one and done poster…