I have been having this problem for a couple weeks now, i can take the pedal to where it stops and feels like a concrete block holding it from going farther. And no tires lock up and just still moves forward. No leaking lines and no fluid is being lost, A mechanic at my work thinks it the brake booster He popped the plug out and said it didnt seem like a lot of pressure came out. what do you guys think

 

sounds like a vacuum leak with the booster
check if the vacuum line is attached
if it is cracked or broken
if the vacuum check valve is good
all of the above are easier to fix/replace than the booster itself

when the booster is not functioning u only have regular brakes, no power assist, which means u need a heavy right foot

iirc if u pull out the check valve air shouldnt come out, it should go in, thats a sign that the booster is holding the vacuum

 

now how do i check for all the other things, like i said i and push the pedal down then it just stops going down, not letting my tires lock up and anything.

 

start the engine, let it run for a few seconds then shut it off

disconnect the vacuum hose for the brake booster at the brake booster side
you should not hear any air hissing in either direction

then disconnect the check valve from the brake booster
you should hear air rushing inside the brake booster

if it doesnt then theres a leak
if u have a stiff pedal with the engine running at idle then its the booster
if u have a stiff pedal with the engine off but not while running at idle, then its the check valve

 

thanks for the info and how much is the booster

 

hey im having a similiar problem, i can build pressure when the car is off (although i still have no brakes when i put the car in neutral and try braking with car off), however when i turn the car on the pedal goes straight to the floor with barely any resistance

i have replaced all rear brake lines, the front ones are in fine condition with no leaks, changed front brake pads, and even replaced the master cylinder and did several complete bleeding jobs until there was no air (from the master cylinder and all brake lines)

we checked the the vaccuum, booster, and check valve according to the procedure respectirocz posted in post #4 and everything checked out fine, no hissing when we pulled the hose, but when we pulled the check valve we heard the rush of air.

me and my buddy are so lost right now...any ideas?