Hey guys,
I just recently installed a wilwood 4 piston big brake kit on my 2000 Si.
after replacing the calipers/rotors i bled the system using a mac tools vacuum bleeder. It seemed to get all of the air out. yet when i push the brake pedal with the car running it feels spongy and goes down about 2/3 of the way with no resistance, even when the pedal hits resistance i can keep pushing it.

So naturally my first reaction was that there was still air in the lines, so i bled all 4 corners with the vacuum bleeder....no better. so i gravity bled all 4 corners, no air bubbles from the rear, and a few from the front. still the pedal feels the same.

I was leaning towards torn seals in the master cylinder from pumping the brakes without a piece of wood under the pedal to keep it in its normal travel range. (mistake i know, just slipped my mind) although the pedal stays up and firm when the engine is off. (the pedal moves down slightly before i hit resistance. could the effect just be amplified when the brake booster is working? causing the excessive free play in the pedal?)

as far as i know my master cylinder did not run dry while changing the calipers, at least thats what my friends say.

so next step is to remove the master cylinder, disassemble it and inspect the seals. if the seals are not blatantly damaged i will bench bleed the master i try again.

Am i heading on the right track?
any input would be great guys, thanks!

 

I wish I could help because after I installed the Wilwood 6 piston kit (front and rear) I had a similar problem bleeding the brake's on my Type R. But I can't recall the step by step process I did to eventually get them bled.

You might have a bigger problem but I would keep trying to bleed them before I go to all that trouble you've described. Good luck.

 

You're adding a lot more piston area with the same amount of master cylinder fluid movement. It takes much more fluid to push out that extra piston area so naturally it'll take much more pedal movement.

Stepping up to a larger master cylinder (1") will push more fluid with the same pedal travel. You might not ever get that "stock pedal feel" but it'll be much better than what you have now.

 

Interesting! Do you have any suggestion as to which master cylinder is 1" and will fit his si, maybe the Type R or Legend? I might want to look into upgrading also even though mine aren't too bad.

 

I'm running an ABS-DC2 1" master cylinder on my 1996 hatch with the 12.2" Wilwood 4 piston kit. Pedal travel and feel are very close to stock.

I'm running an EG6 15/16" master cylinder on my 1992 hatch with Spoon 4 piston calipers and the pedal travel is a lot further compared to stock (or my EK.)

 

thanks phunhaus, thats the same wilwood kit i have.
i just picked up a 1" master cylinder about 30 minutes ago.
i going to go out and rebleed the whole system one last time, and if it stays the same fire the new master in.

any tips for the MC install? other then to bench bleed it?

 

make sure to bleed the inner side of the wilwood caliper first then the outer, this is only first time you put them on to make sure you get all air out

 

I have a different problem then you do now with my 99 EX. I can't even push my car after I install the brake pads on my Wilwood kit. I talked to Wilwood about it and they said that I need to either adjust my brake pedal attached to the brake booster or my caliper is not straight with the rotor. I did notice the pad is not lying flat against the rotor. It only touches the rotor at two points. Did you have any problems like that?

I upgraded my rear brakes to disc so I also upgraded my master cylinder and proportional valve to the SI ones. They said that was all I needed to do and it should work fine. Also, be sure to bleed only the top two bleeders on the caliper. I thought you had to bleed from the outside first then the inside?

 

Thanks for all the help guys.
i ended up going with an ITR master cylinder and after bleeding the system from the install of that it feels great!