I have searched this forum high and low but I haven't found anything that I haven't tried yet. Here's the story. I have a 2004 GTP and I replaced all 4 rotors and pads. During the process of pushing the front drivers side piston back in the caliper I forgot to crack the bleeder valve and blew my master cylinder. It started leaking out the back of the MC and my pedal would hold firm for a moment and go straight to the floor. My stupidity cost me $75 bucks and I move on.
I bench bleed the new MC and install it on the car. I even bleed it a few times on the car by having somebody hold the pedal down while I crack open the hose fittings just to be sure. I ran two quarts of brake fluid through the thing and the pedal was still doing the exact same thing, holding firm for a moment and then fading to the floor. No residual air was flowing out during bleeding.
So I do some more research and realize since I introduced air into the system before the ABS module I need to have a special computer to cycle it while I bleed it. So I have my buddy come out, ASE certified in everything I believe, and help me bleed the system with his computer. His pressure bleeder just broke so we did it the old fashioned way, pumping and cracking the valves as the computer cycled the module. After about a half an hour of bleeding nothing got better. He told me the MC I just put on was probably junk and to get a new one, so I did. I installed it using the same procedure mentioned above and bench bled it.
My buddy is busy and hasn't made it back out for a second bleeding round with the computer yet but the same issues persist. I pump the pedal a few times to get it firm and after a second of pressure it drops to the floor. I know there is air in the system but I have no clue why it's going to the floor like this. It can't be two MC's in a row that are junk so I think I'm missing something here. All brake pads are making contact with the rotors too. I took it out for a drive and the pads left their contact patch.
On a side note, when the car is off the pedal holds firm and doesn't hit the floor. When I turn the car on the pedal drops to the floor as described above. I also gave a mighty crank to the passenger side rear caliper with a C-clamp to push it back in before I realized they had to be screwed back in. I don't know if that would cause some sort of damage or not.
Any help would be appreciated.
If I don't get it figured out soon I'd like to make an offer to trade it for a somebodies newer GXP with more modifications and less miles with brakes that work