In the first instance of this problem, my brake pedal was stuck to the floor. By pumping it a few times, it gradually released and rose to the proper level. Brakes then seemed to work fine for a couple of weeks, until I reversed out of a parking space, but could not brake the car when I shifted into drive. I pushed the brake pedal to the floor, but could not stop until I ran over two large boulders that, thankfully, stopped the car short of a big tree.
My mechanic doesn’t know exactly what went wrong, but is replacing the brake cylinder. I fervently hope that fixes the problem! What could it be?
“replacing the brake cylinder” . . . I take it you mean the brake master cylinder?
When this incident occurred, was the pedal soft or rock hard?
If it was soft, you definitely have air in the system
If it was rock hard, you have a vacuum problem . . . most likely the booster or the hose
In any case, after replacing that master cylinder, I would advise the mechanic to very carefully inspect all of the brake lines, hoses and calipers
And I would also advise that mechanic to bleed the brakes using a diaphragm brake bleeder and the appropriate adapter. It is more effective than the two man method
Most people panic and forget they even have a hand brake. (Could also be a foot operated parking brake, even harder to do when you are freaking out that your car can’t stop)