I just had my front brake rotors resurfaced due to some pulsating while braking. Disassembly requires disconnecting the hydraulic line from each caliper on my setup (older wilwood arizona z car kit). I put everything back together with fresh pads and flat rotors this weekend and started bleeding the lines, but I hear an air "breathing" noise when pumping the petal. Here is a video of me pumping the brakes https://imgur.com/a/w5kBNBj. Please excuse my fumbling with the pedals, it's hard to video and pump the brakes while standing on one leg. The brake petal also won't stay firm. It will firm up when you pump it, but get soft after a bit of doing nothing. The petal was firm and worked great before this rotor project. I have:
"bench" bleed the master (on the car).
gravity bleed the lines.
used a one-man vacuum bleeder.
had my wife help me do the ol 2 person bleeding procedure on all 4 corners and I still get this noise.
This isn't my first time bleeding brakes and have done them successfully on this car before. Other things I checked/tried:
It's not leaking fluid anywhere.
There are no bubbles in the lines when I bleed them.
I checked and tightened the vacuum line to the booster.
Replaced the check valve with a new one I had in my parts stash with no luck.
Has anyone seen this before? I'm assuming it's a bad booster or master, but was hoping for some advise before I start ordering parts. Could draining the master have created a leak due to old seals or something? It looks like a booster would have to be rebuilt too since they are not available. I have a 7" early 240 style booster with a 15/16 MC. It's driving season where I live and am hoping to get back on the road asap!