After installing a new master cylinder / power booster my brakes worked great but will nearly lock up when when driving stop and go. My pedal is up and all 4 wheels are tight. I have to either readjust the push rod or wait for the pedal to go back to normal. Problem seems to be with the master cylinder. Disconnecting the vacuum doesn't help. This is an all drum application with no proportioning value needed. Perplexed.
