Alright, I picked up a 1990 Audi 100. 5L 2.3 with ABS.

Since I've had the car, to stop I need to floor the breaks. No pressure under the pedal.

This pretty much has to be the master cylinder, right?

I tried bleeding the system, manually. When the brakes were pumped no pressure was ever built up. (tried with the car running and off)

Also, while bleeding the system, all the calipers bled the fluid like the should except for the the driver side front. Attemps to bleed from the master cylinder also failed and nothing came out of the valve.

Any ideas?

 

Alright, for reference sake, the problem was the master brake cylinder.

It was a bi*ch to track down the proper one, but after that it was a really smooth replacment.

Also, it turned out the back brakes were not even functioning before!

Now, everything works great and with proper pressure.

-nc