93 Lumina 3.1 with ABS. Brake problem

[GSX4]

While filling up at the gas station the other day, I noticed something wet trickling down the drivers side rear wheel rim. Thinking it was water at first I ignored it. Then I had a bad feeling, but decided to check it.... and it was Brake fluid. I limped the car home and checked tha master cylinder and it was low. So luckily for me and anyone else on the road no accident happened. It could have been much worse. Anyway, took the rim off and the caliper was leaking. Incidentally, this was replaced last summer when I did full brake job and replaced ALL four rotors caliopers etc. Anyway, I put the new one in today, and had to bleed the system as per the Haynes manual, and cannot get a hard brake pedal anymore. Incidentally, my wife drove the car a few times before and said the pedal was acting funny, but seemed alright.
I am using a MOTIVE power bleeder and following all directions to bleed the ABS system correctly. THere is no air in the system, and I am certain of that.

That said, I am now suspecting the master cylinder is shot. Unfortunately, the maser cylinder in this model has the ABS controller attached. I have not even begun to check into what they run for as I am not really thrilled about having to spend a ton of dough for it. Does anyone know what this would typically run for? Is it something I should let a shop do due to the ABS system? Personally, I have the skills to do this, but not to seperate the ABS unit and master cylinder. I have to believe there are rebuilt units out there, but need some advise on whether this is the correct course to take? Any ideas would be appreciated.

[maxwedge]

Try bleeding the ports on the abs unit, rear one first. Also unless the cylinder was dry down to the bypass port, you shouldn't have had this problem. In the future when doing brake work pinch off the hose to prevent draining the system, makes it easier to bleed the system.

[GSX4]

I did bleed the ABS unit as per the manual. I bled the whole car and ABS Unit a total of 5 times. The thing still won't give me a hard pedal. I am suspecting the master cylinder.

[maxwedge]

Remember sitting still the pedal can feel spongy, how is it driving.

[GSX4]

It is terrible when driving. The pedal goes to the floor and provides minimal braking force. It's scary actually! Last time I went out and checked it, and it was about 7fahrenheit. I live in MN. I can pump up the pedal to get a firm pedal pressure, but as soon as you start the car, the pedal goes to the floor and if you pump the pedal when the engine is running, you can get to a point where the pedal stiffens up a little, but it does not stay there, and at times the pedal goes straight to the floor. One time when I did this, the ABS light came on. This seems like it's a master cylinder issue. Might have fluid past the first seal.

[Carwhiz]

Sounds like a bad master cylinder, check for any signs of leaking on the underside of the cylinder. I'm surprised your abs still works!! This is the first lumina i've came across that still has a functioning abs for some time! My wheel sensors gave out about 115K and so i disconnected the ABS system and I've been driving on conventional brakes for 100K now. here in minnesota the salt eats up the sensors pretty bad~! But anyways, you have all new brakes at the wheels, my guess is a bad master cylinder.

[GSX4]

It was a bad master cylinder. I found a rebuilt master cylinder/ABS unit for $340 and reused the black ABS module (the black plastic box with 3 cogs that mesh into 3 gears on the ABS pump.) from teh old unit. It was a straight swap. Took me roughly 2 hours including a trip to sears to buy a 12mm no round off wrench as the brake wrench stripped one of hte nuts! Anyway, I managed to crack them all loose, and then it was easy progress until it was time to blee the brakes. I tried bench bleeding the new unit as stated in my Haynes manual. That seemed to work. Then I bolted the unit in, and attached my Motive Power Bleeder. I pressurized the system to 15 pounds and started the usual trip around the car to bleed the zerks starting with Master cylinder first, then rear right, rear left, front right, and front left, then back thte ABS again. I could not get anything out of the rear zerks for some reason. After calling it quits, I limped the car to a garage the next day, and they were able to do a power bleed for $50 and it was as good as new again. She is alive!