May be completely different, but I had the same symptoms occur with a Chrysler Minivan years ago...it was due to a failure of the ABS system.

 

It is my understanding that the ABS could fail, but the brake pedal should not be affected. The wheels will lock up a lot easier,without the ABS, but the pedal shouldn't go to the floor.

 

never had them go all the way to the floor, but, I found I had excellent brakes when I pumped them a few times. Took the car to the dealer (under warranty) and they replaced the master cylinder. Breaks were great for about 4 months then the same issue again. Car is out of the extended warranty now so guess I'll just live with it unless it gets a lot worse. (2012 Performance)

 

Yeah....I was told the same thing. However, I pulled into a rest stop on vacation and as I gently stopped, the pedal went to the floor. Had van towed to dealer who replaced defective Bendix ABS. Chrysler hit with lawsuit: http://www.autonews.com/article/19950918/ANA/509180736/mo.-class-suit-targets-chrysler-abs

That ABS failure, 2 transmission failures and the paint began peeling off the car due to improper prepping at the factory (not covered by Chrysler). All within 5 years. I sold the POS and will never own another Chrysler product.

 

I would check if there's any leaks/loose lines/caliper etc. in the system first, then if all fine I would look into the ABS pump, the pump itself has valves and actuators that can cause this problem over time depends on mileage and brake fluid quality. Master cylinder is a possibility but I would look at that last. I used to work for Ford/Toyota and this guy pretty much explains it all (https://www.youtube.com/watch?v=0r46_unyYk8) all ABS systems these days are similar across most brands and are made by the same few suppliers. I haven't played around with the GM GDS2 software (their factory scan tool dealership uses) but I believe there might be functions in there the technician can test out the ABS valves manually.

Please note the brake fluid really should be changed every two to three years or 20-30k miles. DOT3 fluid is hygroscopic and over time these fluid attracts moisture the fluid will loose its ability to lubricate and prevent rust to the brake components including the ABS pump and can cause premature wear. I read somewhere the AC Delco original brake fluid might have some special additives that might push it to 5 years 50k under ideal condition but I would change it before that consider the humid climate during summer by me. When I was working at the dealership many of the brake problems I encountered can be somewhat tracked down to brake fluid have never been replaced, when brake fluid wears out it looses the ability to protect and lubricate, worst one I've seen is green algae in brake reservoir, that just tells me the brake system was mostly water.

 

brakes completely bottomed out after hitting a small bump.

Just dealt with this. I bet you were braking in slippery conditions when you it the bump. Your ABS activated, but a valve in the ABS module stuck open. The pedal goes to the floor (almost).

In my case, the soft pedal condition persisted until I turned off the car, got out, and got back in some time later to investigate. At that time the brakes acted normally until I activated ABS and the condition returned.

Brake fluid had not been changed in several years. I changed the fluid and changed the pads to a different brand of ceramic (to change the ABS response of the system). I them "exercised" the ABS system with a dozen or so attempted lock ups to verify the system was working normally again. I then bled the brakes one more time to get out any crap that could have knock out of the ABS controller.

There are electronic devices you can buy that will activate the ABS solenoids during the fluid change to help flush the module. An Ebay version I saw was about $35.

Anyway, things seem normal again. And I have since changed the fluid in my other cars.

 

Same thing multiple times for me. After car wash, failure. Hit a bump, failure. No codes. Turn car off, and wait 10 minutes, then there’s no problem.

 

have the fluid changed and a ABS bleed... any GM dealer can do this.. its kinda dangerous, i had mine done...