Hey guys I'm in need of some help with this problem , the vehicle is a 2000 chevy s10 blazer 4x4 . And sometimes the brakes just go right to the floor , most of the time they worked fine . Also they were pulsating pretty bad . The things I have done so far tonight changed front pads and rotors and cleaned everything under the vehicle . I'm thinking the master cylinder is the culprit but figured I'd ask for your opinion , thanks for any input you can give . Also it sounds like the rear caliper on the driverside is letting the brake pads wiggle in there.

 

Sounds like a master cylinder to me. Probably a leaking seal internally. Also have you checked the vacuum lines? Loss of vacuum can cause dead dead pedal issues as well.

 

rex pretty much covered it, start by checking vac lines, specifically the one that comes off the brake booster to the intake, if that is fine, and all other vac lines are fine, next, like he said, the master.

 

Another thought is if the rpms drop when you press the brake pedal the brake booster could even be going bad.

 

Ok I found a line that was leaking , witch I think I did trying to find something else wrong . I changed that line and bleed the system ,, still no brakes . So I replaced the master cylinder and bleed the system again , and I still have no pedal . The brake booster is working fine and you can see all 4 calipers working and with it jacked up in 4x4 it does stop the wheels but the pedal goes to the floor . I'll keep you posted if I find anything .

 

I cracked the bleeders on all the brake calipers and let the fluid flow while I picked up all the tools and then closed them all back up and now I have brakes again , weird ,

 

Probably has air trapped in the EBCM solenoids. You'll need to do the automated bleed and then bleed all 4 wheels, (in that order). You'll need a scan tool capable of initiating the automated bleed, (auto parts stores don't have them).