Vehicle is a 2013 Edge (bought it used 3 years ago & it has been a crappy vehicle) & yesterday my wife was driving & applied the brake pedal & it went all the way to the floor & labored to stop - she did not try to pump it up. Then everything returned to normal. I drove it after she got home & brakes seemed normal. Earlier today she drove it again, & no issues.

The brake booster went bad about a year ago (they basically ALL do on Edges & some other Phords) & there was a TSB on it, so Phord replaced it for no charge. *There are multiple things that fail on these vehicles prematurely & Phord knows about them, so they replace them well after the warranty period, but they are not at recall level.

Anyway, any ideas on the braking issue?

Had a used one at the jeep store a while back and it had really low pedal , tried a new master and checked every thing I could.I suspected somthing wonky in the ABS system like internal leakage. Didnt have the correct scanner to do anything with it so we sent it the Ford store and I never heard back about it.

I just bought a code reader at O'reilly's that reads ABS codes, cost me $100.

https://tinyurl.com/5avb6cvu

Id start with that.

When I was writing service at a Ford store (HOLY %^#*, that was 20 years ago...I'm getting old), we had an Expedition that almost rolled into traffic on a major highway with the driver and her 3 kids. She said the brakes worked great slowing form 50 MPH down to about 5 mph, then the pedal went to the floor and it slowly rolled ahead (luckily she threw it into reverse and then Park). Turns out the ABS was getting a speed reading and thought the brakes were locking up, so it bled the pressure off until they started turning again. Not good when you're at a stop sign... Not clear from your post whether this was high or low speed, but just another possibility. I second checking for codes, but see if you can read live data to check sensors as well.

Just asked my wife a few more specifics about this. She was driving maybe 25 when it happened - on a dirt road that leads into our subdivision, also no dash light/no brake failure light. Question is, is Ford liable in any way if the ABS unit fails, or is this a "wear" part that coverage expires on when the vehicle warranty expires?

UPDATE: Check out this video & read the comments below it - I think this is what happened: https://youtu.be/tBBlLj8-U7Q

This is just another reason why I'll never buy another Ford product. I've never had weird crap like this happen with any Chrysler product I've ever owned. I'm going to call the dealer that replaced the brake booster & see if there is a silent recall on these units.

I've seen something similar (in a mid-80's Dodge pick-up). Try this: Get going about 30MPH and depress the brake VERY gently and see if you can get it to duplicate. In my experience it was a bad master cylinder...

That reader I linked does live data.

This

I have had numerous ABS systems trip with messed up sensor data. It is not uncommon for the open reluctor sensors to pick up metal filings from the brakes/road since they are magnetic and it freaks the sensor out. Clean them with brake clean and wipe them with a paper towel to get the filings off. This is for the open sensors with the exposed tone wheel/reluctor. Sensors embedded in a sealed wheel bearing require a scan tool to check them.

Often the wiring starts to go bad where it flexes at the control arm or ball joint and causes similar problems but those usually trip the ABS light since the sensor signal goes completly silent and not just erratic but anything is possible.

If it happens often and you can reproduce the problem then disconnect the ABS unit and see if it goes away. If so then it is a sensor/pump/controller problem. If not then start looking at the hydraulics/booster.

Hope it helps.