Woah! Nelly!

[ckhd]

OK, the Suburban's name isn't "Nelly", but yelling "WOAH!" would have done more to stop me than my brakes!

A little history:
I bought this 'burb about a month ago. The guy I bought it from said there was a problem with the brakes. He told me he had done the following: New master cylinder X 2, new brake booster X 2, "professional" did the four corners, new vacuum check valve, and none of it took care of the problem.

Here's what happened... I was headed into town this morning, and just as I was getting in to town, a dumb dog ran out in front of me. I tried a 'panic stop' to avoid the mutt, but I might as well not even hit the brakes. I was able to swerve to miss the dog, but don't know what happened to the brakes. The pedal was hard as a rock, and barely provided any slowing. I was practically standing on the pedal.

Normally, the brakes work great. I'm used to non-power brakes, and so I brake way ahead of time, and usually use gentle, steady pressure, or gentle pumps. When I jabbed them to try to miss the dog, there just weren't any brakes. 100 yard later, doing my normal stop, the brakes worked just fine.

Anyone know why it would do this? What isn't right?

I'm just glad that I wasn't trying to avoid a car, I wouldn't have been able to miss it...