Brake issue.

[rockyrivermark]

1971 c10. 350/350
Front disc brakes rear drum. Power brakes
I added a rear disc conversion this evening from little shop mfg.
kit install well bit had some problems after bleeding

New master cylinder last year.
All new stainless lines last year.
So I bleed the whole system after the rear disc conversion And now pedal is low and I have air hissing sound from master/booster area when I push the pedal down. Any thoughts on that?
I don't think I went to low on fluid in master when bleeding but prob close.
Everything bled fine.
The proportioning valve was disc drum so directions said to take the rubber piece out of prop valve for disc disc
Possibly bench bleed master in case fluid go too Low when bleeding?
Any info appreciated!
Thanks Mark

[RedRider]

Hey Mark, don’t know if this is helpful but I went through a mess of troubleshooting with my brakes, and was getting that hissing sound as well . Turns out my NEW master cylinder was faulty. Installed another one and problem solved.

[rockyrivermark]

Originally Posted by RedRider

Hey Mark, don’t know if this is helpful but I went through a mess of troubleshooting with my brakes, and was getting that hissing sound as well . Turns out my NEW master cylinder was faulty. Installed another one and problem solved.

Thanks. Lifetime warranty on the master. Changing it tonight
I'll post back if that was it
Thanks
Mark