So did the vac at the resi work? Good to go? I hate them slaves with a passion. I had to give up messing with them.
Old methods:
Pulled that master out, stretch it on a post, and bled it, then throw it back in. If it still gives me heck, I gravity bled it with a fluid feed bottle. If that doesn't do it (even with tapping the lines), then the mityvac gets used, drawing air out at the slave. If that didn't work start all over, check O-rings, and put it back on the post. Blah......
New method:
Buy a new Pre-bled master, and flip the bird to the old one. I actually did that on my last install. Worked perfectly. Didn't even get my hands dirty. lol