there was a sponge pedal and could not understand what was the reason. No leaks, new pads. Switched this master cylinder to my Sierra and the pedal is much better. Since GM has stopped replacing them at the factory, this works perfectly. Don't forget to upgrade this unit on the time bank. Hopefully the stainless steel brake hoses will take care of the rest of the sponge pedal. UPDATE A few years later I'm back to square one. sponge pedal. Everything bled dry, gone over and over again. I'll try another MC and hope this is the culprit