OK, I'm new to this forum, but not new to the game. I am a former professional mechanic, so I have a background. I have searched the forum and found alot of info for soft brakes, leaking brakes, etc, but not much for hard brakes. Here is the history of this vehicle: It is a 96 GMC Jimmy with the 4.3 auto, 4x4, ABS. Vehicle has right at 140K. I recently changed the engine, replaced brake lines that were about to blow on the front while the engine was out. After returning the vehicle to my sister, she blew the rear line on the axle out, hence the rest of the lines replaced and bled. New wheel cylinders, and calipers, too. Brakes again bled. Good hard pedal during bleeding. Problem became that the pedal stays hard all the time, as if the brake booster were bad. I replaced the booster, same issue. Changed the booster again, thinking I got a bad one, same issue. Run the engine and pull the line out of the booster and it sucks vaccum as it should. Now I am stumped. Any current auto techs out there that have seen this and can help me out? My sis has little money and I am now lost. Thanks in advance.

 

Wow,i was thinking "this'll be easy" now im brain dead.

Im wondering if there is a restriction in the master cylinder or abs system. Could had some dirt in the fluid,and from all this bleeding it has clogged a hole somewhere.

 

Exactly my problem. I've done this for years, but it's been years since working as a mechanic. This thing was new when I got out of it professionally. My head hurts... Wondering if the ABS could have anything to do with it. Never bled it, got good flow at all wheels bleeding normally, so didn't.

 

the abs in these 90s blazers nowadays has always had problems. a reman'd one is like 700-1000 bucks. you can always hit up junk yards etc. gamble and get lucky. My current blazer had soft pedal issues. then one day it fixed its self. not sure if i wanna worry about it or not as i have nice firm brakes. lol

 

Flex hoses? We replace quite a few because the clamps that hold then to the a-arm has rust build up and it crushes the hose.

 

I should add if it is in fact the ABS module that's the problem, I have one here that you can have for the cost of shipping. It's from my '96. '96 has a unique ABS system.

 

thats possible. when i was trying to figure out a braking issue on a customers tahoe i clamped both front lines and that pedal was at the dead top and stopped hard. even if they bled out easily sometimes they dont return the fluid easily

also another issue i see with a lot of chevys is the pads love to rot into the slides causing them not to slide back causing a harder brake pedal but if you replaced the calipers im guessing the bracket and slides are new too.

 

I appreciate the thoughts so far. Haven't had time to breathe (work is crazy busy) much less look at it. I will check out those ideas when I can. Meantime, if anyone else has had any experiences like this, feel free to hit me in the head with it. A hand grenade is looking mighty fine, about now...

 

Hoses will get old and soft and implode on themselfs

 

UPDATE: Turned out that the 2 used boosters I got were both bad. Sis bought a remanufactured one and it works great. Glad that is over-with! Thanks to all who offered up thoughts and wisdom! And I am now an "expert" at changing these...took me about half an hour.

Jim