Posted in the EG forum first, but you guys are the bomb when it comes to brakes, so i figured id give it a hand here too

This has been happening since I swapped all of my brake and suspension gear from my old shell to my new CX
I have full GSR brakes, and i even swapped master cylinders because mine was still good on the old car. I didnt bleed the Master Cylinder before removing it. Car has SS brake Lines too. After a full bleeding, the brake was still extremely low. Iv bled the brakes properly about 3 times since. After the 2nd time, the car was a little more drivable, but now it starts off being still, and then it varies, from somewhat stiff one on brake attempt, to practically hitting the floor on others. Im almost 100% that there is no air in the lines. Could it be that the master cylinder has gone bad? Maybe the brake booster? Any other ideas?

 

Does it build any pressure when pumping the pedal?

 

all i can think of is the master cylinder (13/16th i believe) has gone bad somehow, and ill swap it with my gsr booster/cylinder
but its not leaking any fluid, so its extremely weird

 

no, not when the car is on, it will be firm when im stopped most of the time, and most of the time when i am driving it will feel like im stepping on a sponge

i went through two of the big bottles of brake fluid today, i couldnt bleed my brakes anymore if i tried, but i will though
im gonna change the booster and cylinder the a gsr one i have laying around
then ill bleed them with a clear line so i can see for sure if any air is being left inside

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CuttingEdge SI &raquo;</TD></TR><TR><TD CLASS="quote">no, not when the car is on, it will be firm when im stopped most of the time, and most of the time when i am driving it will feel like im stepping on a sponge

i went through two of the big bottles of brake fluid today, i couldnt bleed my brakes anymore if i tried, but i will though
im gonna change the booster and cylinder the a gsr one i have laying around
then ill bleed them with a clear line so i can see for sure if any air is being left inside </TD></TR></TABLE>

Gotta be master cylinder. Cheap rebuilt kit, at least.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CuttingEdge SI &raquo;</TD></TR><TR><TD CLASS="quote">no, not when the car is on, it will be firm when im stopped most of the time, and most of the time when i am driving it will feel like im stepping on a sponge
</TD></TR></TABLE>

it is a long shot, but if you have double checked the system for leaks, replaced/rebuilt all master and slaves, then you might want to check your bearings and hubs. A long pedal while driving can indicate knock-back. If this is the case, your brakes should recover after one pump and be high again. Happened on our civic, it was troubling to diagnose.

 

Another thing it could possibly be is the MC was not primed. If you installed it without priming it, it would be VERY hard to get all the air out of the MC without priming it!
I would try taking it off, priming it, bleed brakes again, and then see if it works. If it's still the same, then it's probably just the MC is bad.


Keep in mind, when your talking about a leaking MC, it's not actually leaking fluid that you can see on the ground. At least most of the time when we talk about this, it means that the MC is allowing fluid to go by the seals and not really build the pressure it should! Sometimes if you step on the pedal and hold it, it will slowly go to the floor. This is a CLEAR sign that something is obviously wrong and it can turn out to be a leaking MC! It could be other things, but the MC can do some funny things!