dualquadpete

My 69 Cutlass "appears" to have a fairly new booster [gold anodized] but on first start there is a hissing on brake application from under dash & pedal is "hard: & almost no brakes??? 5 minutes later no hiss & brakes work fine ???? Booster?? Rod adjustment?? Car has been changed to discs up front, new master[appears to be] new proportioning valve [looks new] car stops great after a couple of minutes of driving???