It was a 90 degree day and I had a 3 and a half mile stop and go trip to reach the turnpike. Just before reaching the turnpike is an uphill “S” shaped ram that joins another road that merges the two together. Traffic always backs up there to a stop. About ½ mile down the 3.5 mile portion, every time I put my foot on the brakes, the ABS Pump would run continuously, only stopping when releasing the brakes. The press and release with the pump running happened at least 50 times. Climbing the ramp and making the last right hand turn I was moving in inches not feet. When I complete the merge and all the wheels were straight ( and fortunately 10 feet from the car in front of me) upon the next brake pedal push the pedal went all the way to the floor and would not pump up. I managed to pull over to the side of the road into a parking lot( still no pedal). I called a towing service which took about 1hr and 45 minutes to get there. I helped the flatbed driver by driving the car while he pulled up on the cable. I had no reason to touch the brakes. At my house I jumped in the car to steer it while being let down on the bed. When the car reached the ground I instinctively went for the brake pedal and It was fine. I could not make it go down to the floor. I tested the system with the correct ABS tester (4 X’s) and found nothing. I am afraid to drive the car….any suggestions?

Sounds like the master cylinder is leaking internally. When is the last time you changed the fluid or replaced any components? Brake boosters can also go bad with heat but I'd bet mc first. Also, I'm assuming there are no external leaks?

Agree with Matatk. Fresh master & a complete fluid flush/change. Brake fluid collects moisture over time which equates to a lower fluid boiling point = loss of pressure.

Valvoline synthetic brake fluid works well for me.

My alternate guess would be a caliper problem on one of the wheels maybe?

The only thing separating the two circuits in the master cylinder is an o-ring.

If you haven't replaced the master cylinder in a while, you may want to at least check it.

Well, I guess I will go looking for a master cylinder and do a brake flush....There are no leaks...Thanks for the help from everyone

check for weaping where the master meets the booster.