Out of ideas, pedal to the floor

[donkason]

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

[RyanL]

thats weird that it holds the pressure and then drops. are you sure your brake fluid isnt leaking from somewhere? you should monitor the level. if not well one way to stiffen the pedal is to remove the shims from the brake pads.

[Steel Armadillo]

You mean you forced something with threads straight in instead using the threads?

[Ridin ON Chrome]

You mean you forced something with threads straight in instead using the threads?

I didnt read all that, but that um doesnt sound good.


all your lines look good, the ones by the MC too? The SS braided ones?

[foursixer]

if the system have no leaks, try gravity bleeding. fill the master all the way up. open all the bleeder screws on the calipers and let it sit for about 30-45mins. monitor the brake fluid level in the master cylinder that all the fluid dont leak out and top off if needed. last, close all the screws and bleed a final time starting with the wheel farthest away from the master cylinder. let us know if that works!

[donkason]

I did force the piston in the caliper. Luckily my C-clamp has a swivel on it so the pressure let it spin into place,so no damage done. The caliper is grabbing the rotor too.

I haven't found a leak and the fluid level is stable.

I'll try the gravity bleeding and see how it goes. Out of curiosity, what's the major difference or advantage to gravity bleeding as opposed to traditional methods? I've never heard of gravity bleeding until now so I'm always happy to learn something new.

Thanks!

[donkason]

I did force the piston in the caliper. Luckily my C-clamp has a swivel on it so the pressure let it spin into place,so no damage done. The caliper is grabbing the rotor too.

I haven't found a leak and the fluid level is stable.

I'll try the gravity bleeding and see how it goes. Out of curiosity, what's the major difference or advantage to gravity bleeding as opposed to traditional methods? I've never heard of gravity bleeding until now so I'm always happy to learn something new.

Thanks!

[foursixer]

gravity bleeding is good when all else fails. it more than less slowly allow the fluid to take the space off air, but by no means this be your final step. once you get fluid flowing out all calipers by mere gravity. close all the bleeder screws and bleed the system the normal way as mention.

[donkason]

I think that did the trick. Gravity bled for a half quart and did traditional bleeding. Pedal still falls a bit low when I'm in neutral pumping it, but on the road the hawk pads are biting like a dog on a bone and the pedal feels fine. ABS works like it's supposed to. Good to go.

I'll keep the gravity bleeding in my back pocket from now on. Thank you for all your help folks.

Now onto the homemade intake and strut tower braces.

[donkason]

I think that did the trick. Gravity bled for a half quart and did traditional bleeding. Pedal still falls a bit low when I'm in neutral pumping it, but on the road the hawk pads are biting like a dog on a bone and the pedal feels fine. I don't think there's any air left in the system since it doesnt get any firmer as I pump. ABS works like it's supposed to. Good to go.

I'll keep the gravity bleeding in my back pocket from now on. Thank you for all your help folks.

Now onto the homemade intake and strut tower braces.

[RyanL]

when your pumping with the engine running the pedal will always fall to the ground! its normal