what did I do wrong? still brake issue

[red91efhatch]

I know it's getting old me and my brakes.... but now i'm running into an issue where after driving the car from 10-20 minutes the pedal gets rock hard and all four wheels lock up. here's my setup where did I go wrong?Rear disc conversion from DA,Stock EF front calipers,DA non abs 40/40 prop valve,ef civic EX 15/16 bore master cylinder,brake booster ef civic EX, now I am planning on adding the DA front calipers anyone know what may be causing all four to lock up and pedal stiff? any advice is appreciated

 

[George777]

My Civic would sometimes do that. I narrowed it down to a vacuum problem.

 

[red91efhatch]

My Civic would sometimes do that. I narrowed it down to a vacuum problem.

ok, care to elaborate? I have checked the check valve and seems to flow fine also

 

[George777]

It was a while ago, and I don't know what caused it exactly, but sometimes the pedal would just get stiff as hell. I could rev the motor a little bit and it would soften. We deduced it was a vacuum leak, because under higher rpm's it was fine, but once it got to an idle it would get hard again. I sold the car, so I never really looked into it more than that...

 

[ntenc1]

check valve on the brake booster is probrably letting air into the booster killing the vacuum which it operates off of when the car is sitting.

 

[94H_Ex]

yeah that little valve in your brake boosters vacuum line can cause that problem.