I have been having a problem with poor braking performance. I can't get the car to stop, it just slows down quickly. The pedal does not feel as firm as it always did.

I tried replacing all 4 rotors, new ceramic pads on all 4 wheels (needed them anyway), 4 new brake hoses and installed a brand new AC Delco master cylinder.

I have bled the brakes in the proper sequence (including the ABS bleeder screws) about 6 times and even purchased a pressure bleeder and bled them with that. There is no air in the system. I have not taken it to the dealer to activate the ABS unit during bleeding.

I did notice some black specs in the fluid when I bled the right rear wheel.

The brakes still have no stopping power. They feel firm when the car is not running. With the engine running and when I press and hold the brake pedal, I can feel the pedal slowly start to drop away all the way to the floor.

I am not losing any fluid anywhere and all 4 wheel cylinders are dry with no signs of leakage.

The brakes get hard to press when I remove the vacuum line from the booster so I know that is working OK.

Could this be the ABS unit? Can anyone help me diagnose? I am not getting any ABS or other lights.

 

Given what you have replaced, you still may have air, or dirty fluid as I do not see where you flushed the brake fluid.

 

Every time I bled the brakes, I completeley flushed them with brand new Valvoline Synthetic (DOT 3 or 4). Must have gone through 3 gallons of the stuff.

Took it for a test drive last night and it is much better than it was. I noticed a liitle wetness between the MC and the booster. Not sure if this is left over spillage or if the new MC is leaking. I cleaned it up and I am going to drive it a little to see if it comes back.

Pedal still feels spongy to me but now I can get the low Low Traction light to come on during a hard stop on dry pavement. I am not sure if the sinking pedal is still there.