Brakes got spongey and inconsistent on me one day. Acted like a master cylinder going bad. Replaced it along with 2 calipers a lines tht the bleeder stripped on.
bled the brakes starting from farthest. Brakes are stiff and don’t go down anymore when truck is off. But when running they are spongey again. Any ideas on what to do. After replacing the master I come across bench bleeding the master cylinder which I did not know about. Any suggestions!

 

Welcome to chevy - please post your vehicle specs!

 

07 chevy avalanche
4x4

 

Definitely remove the master cylinder and perform a bench bleed. Then re bleed all wheels!