What is wrong and what is the fix, sometimes when Im braking the pedal gets hard on 1998 GMC Jimmy

also makes a hydraulic noise and the brakes dont work, when you push really hard they will work again

by in Mondovi, WI on November 13, 2012
2 answers 6 comments
ANSWER by on November 13, 2012
Check vacuum at brake booster if ok have booster replaced.
COMMENT by on November 13, 2012
I agree with wetry
COMMENT by on November 15, 2012
I agree with goodguy.
COMMENT by on November 15, 2012
If I pull the abs fuse the brakes work fine, would it still be the brake booster?
COMMENT by on November 15, 2012
You didn't mention the ABS light was on! Have the system scanned, lots of sensors, the module, valves ect. it could be. There will be codes if you put the fuse back and drive it then scan. Or leave the fuse out but you will no longer have anti lock brakes. Most common problem is wheel speed sensor(s) or connections. But not the only one.
ANSWER by on November 14, 2012
sounds like power brake booster is bad
COMMENT by on November 14, 2012
where is the brake booster located?
COMMENT by on November 14, 2012
It is the big black round thing behind the master cylinder. Suggest towing to repair shop! I agree with everybody.