2001 Lesabre brake failure

[arrak59]

Brakes on 2001 LeSabre failed this morning. For some reason brake pedal went to floor while driving. Before no problems. Can stop but will not drive until I get this fixed. Lines are fine, no leakage. Reservoir is full but no hydraulic pressure to pedal. Generic manuals are no help. Anyone know of diagnostic procedures to narrow this down?


Thanks

 

[gmfugitt]

My guess would be the master cylinder. I am not sure if there is a way to diagnose this. It could also be air bubbles if you have done recent work and did not get the lines bled good enough.

 

[MelsRegal]

if you are 100% positive that there are no leaks anyway including back of master and the reservoirs are full, the seals on the piston in the master have failed.