braking problems

[damdash]

i have a 98 yukon. My problem is that sometimes when i hit my brakes and hit a bump it seems as if they grind or something. When it rains it does it all the time. Also i've been having a problem with them not stopping correctly(take a lil longer than usual). I bled the brakes today(all the way round) and found that when i got to the drivers front, nothing came out. I opened the screw almost til it came out and still nothing. What could be the problem? i have not noticed any leaks or anything elsewhere.

[maxwedge]

Tough to tell what grind or something means, could be premature ABS actuation, have someone knowledgeable drive the truck.

[damdash]

Any idea why when i tried to bleed the front driver caliper no fluid came out. all the other three points bled fine but when i got to the front driver, nothing.

[maxwedge]

Crack the line going into the flex line and see if there is any fluid.

[yukon6inchlift]

those rubber lines go bad, may be the prob there. the noise maybe from the pads on the brake that was doin all the work is worn.