i replaced the master cylinder because there was no brakes nothing no leaks just pedal went to the floor still stoped but not very well. after i replace ythe master cylinder i can not get it to build up pressure the master cylinder is working put the pedal still goes all the way down no air in the lines i bled all the wheels there not anymore
air it has hydroassist is there a special way you have got to bleed this type of sytem thanks

i replaced the master cylinder because there was no brakes nothing no leaks just pedal went to the floor still stoped but not very well. after i replace ythe master cylinder i can not get it to build up pressure the master cylinder is working put the pedal still goes all the way down no air in the lines i bled all the wheels there not anymore
air it has hydroassist is there a special way you have got to bleed this type of sytem thanks

Did you bench bleed the master cylinder after you installed it but before you connected the brake lines?

yes thin i also bled the brake lines at all 4 wheels

sounds like you have a leaky brake line.....check around the car. I had a wagon version do that to me once....at least it was in my yard.

I checked for leaks with all the wheels off nothing its not using any fluid

I checked for leaks with all the wheels off nothing its not using any fluid

There should be a pushrod in the power booster that makes contact with the pistons on the master cylinder. Did you check to see if that's there? It will have a ball or rounded tip.

yes and it moves like it should

Did your lines bleed well? Were they plugged, maybe? Just some thoughts. Another idea is that you have a defective master...see if you can get another in return....maybe it'll work.

I had this type of problem a few years back on an 80 4dr. For 2 weeks I played around with lines then calipers and wheel cylinders, the metering valve, and Booster only to figure out that the rebuilt master cylinder that was less than 3 months old was bad. I took the one off of the 77 caprice that was waiting for an engine transplant... problem solved. :banghead:

i drained all the fluid out and then filled the resevor and pumped all the fluid out until it came out perfectly clean then pu it back together it works know