'93 S-10 Blazer 4.3L Vortec with Kelsey-Hayes ABS. Three times in the last two weeks I've stepped on the brakesonly to find theyare ROCK-HARD...and no brakes! (Thrilling. Trust me.) Twice I was able to stand on them (thank you for holding, seat bolts) and they finally broke free. With it came a lot of wandering from side to side as though one side grabbed and then the other. One other time I was able to pump them five or six times (who can keep track at a time like that) and they broke free somewhat...at least enough to stop the truck. All three times, the next time I applied the brakes they were normal. I don't see anything wrong in the calipers (excessive rust, misalignment, etc.) Is there some failure mode in the ABS that might cause this?

 

mine make a wierd vibration noise and the whole blazer shakes, it is coming from the rear brakes, i also have a 93.

 

Vibrations while braking would be warped rotors or drums.

For the original poster, check your vacuum hose from the engine to the vacuum booster on the firewall behind the brake fluid resivor. Should be a big hose about 1" in diameter, and go into a fitting on the passengers side of the brake booster. I suspect you have a broken fitting, or a crack in the hose somewhere. Without the vacuum assist, the brakes on these trucks are hard as heck. Almost takes two men and a small boy to apply the brakes without the vacuum assist.

 

Thanks to a clogged EGR and a bad fuel injection assembly, my 93 died while going uphill and the brakes went hard. Fun stuff.

 

ya i've been having similar problems on my 94 and the ABS light is on which means i have no ABS so could be the same for u. im just waiting till it warms up here so i can clean off the ABS sensors or one sensor could be bad.