i have bleed the brakes rear to the front - until clear fluid came out without air bubbles. my problem is that my brake pedal is soft it doesnt stay hard. (when i press brake i can feel rush of air go through the intake manifold out the throttle body. if i hold my hand over the throttle body it will cause pressure.

 

LET ME REWORD THIS ... i changed out my front spindles for another set of gsr brakes---- after i did this my pedal would feel soft as hell (can be pushed all the way to floor without resistance or pressure) even after a good proper bleeding of the brakes... i thought my Master cylinder was bad so i replaced it with a good one and also my check valve.still feels like nothing is there. wondering what else could be a problem besides the booster. or if anyone has any other theories. ?

 

if u got drum breaks on the rear then they need adjusted, if u got pad then check the pad and make sure they are good bc u get pressure n ur pedal from the back breaks

 

i have no idea what you just said on reply... but brakes DONT GRAB AT ALL no way to tell whats wrong i was just posting to prove my self wrong and hopefully someone else had a idea or similar problem. thanks anyway bro. nobody ever replies on h-t unless they got under 1000 posts or they r noobs talking about type r's and b-series and gsr this gsr that jdm things... and how they spent 2000+ on a b16 and lost to a stock scion or something. ill figure it out on my own

 

is the pedal soft only when the car is running? I'm having a similar problem & the brake pedal is pretty stiff with the motor off. What master cylinder did you have before? which one did you get to replace it?

by the air rushing out the manifold I would check to see if the brake booster line is installed correctly with the check valve facing the correct direction. test the check valve too

 

I second that. If air rushes out of the throttle body when you press the brake pedal then the check valve is installed in the wrong direction or it isn't working.