Alright, so longer story short, my driver side brake hose burst. I replace it, along with the passenger side front and go to bleed the brakes. I start with the front passenger and then bleed front driver. Peddle was mushy so i decided to bleed all four sides, RR, LR, FR, LR in that order. The brakes held pressure when the car was off. The problem is once i start it and drive, the brake will loose pressure and i will need to pump it for the brakes to work decently.
Since i was tired of dealing with this, i brought it to a shop, who said that its possible that my master cylinder went bad from age why bleeding it because of corrison (BTW i never let the brake touch the floor). They take a look at it and call me and tell me that all four of my brakes are metal on metal. I brought it back home to look at and they all look low on pad but fine, not to mension why would it be so coincidental that they go bad right after my brake line blew, my brakes worked fine before the brake line blew.

So now i dont know what to do. Any ideas?? Im wondering why they will hold pressure when the car is off but not when the car is on, and if there is a way to determine if the master cylinder is to blame or not... Im trying to get my car ready by sunday so any help is appreciated!

I had also thought to bleed the ABS module, but Rosstechs site says that that is only necessary if the abs module is completely dry.

BTW, B5 pre99 a4, 1.8T, manual tranny..

 

Leaking brake booster?

 

the clutch master/slave cylinders share the same fluid resevoir as the brakes. if you blew a line and had air enter the system, a bubble could have gotten caught in the clutch line. i would try bleeding the slave cylinder (same way you would the brakes, theres a bleeder valve on it). if you are positive the brake pedal never hit the floor you shouldnt have damaged the master cylinder. although it doesnt have to hit the floor to do damage, if it comes within an inch of the floor it still could have.

 

you can blow the master by pumping too hard too. my guess is it hit the floor and blew when the line bust.

 

Wouldnt a bad brake booster cause the brakes to get hard, not soft?? The thing that puzzles me the most is that it will hold pressure just fine when the car is off, and not when its on. The only difference between the two is the fact that the brake booster is on when the car is on, but i always thought if those went bad the brakes got hard to push as if the car were off.