Who's fought Silverado/ Sierra brake problems? and won?
Here's what paul said:
"Has been adding brake fluid ? I've seen several cases where the brake booster would b full of brake fluid .... also seen the front brake lines will collapse on the inside of the rubber brake lines ."
Based on that, I would check to see if the booster has fluid in it. I told him you probably haven't had it long enough to see if it's losing fluid.