Trying to bleed the clutch system after replacing the master and slave. I’ve successfully bled the system before, but not after replacing the cylinders. The fluid level in the reservoir isn’t changing after topping it off, and I’m not getting any pedal pressure or fluid out of the slave. I’m bleeding by pumping the clutch several times, and then holding all the way down with a 2x4. Then I crack the bleeder screw on the slave just enough for fluid/air to escape. Then I close it up and repeat. Nothing but a tiny dribble comes out, and no pressure is building. The reservoir nipple and hose are free from obstruction, so I’m thinking that the new master cylinder may be bad. I tried adjusting the rod where it is attached to the pedal, but nothing changes. Here’s my question: Even if there are multiple leaks in the line between the master and slave, the master should still be pulling fluid out of the reservoir, right? Anyone else had this problem and then fixed it?
Did you bench-bleed the cylinders before installing them? If not, it’s no big deal, but it means you’re in for a long process to bleed now. It’s entirely possible you just haven’t been at it long enough.
I personally like to bleed clutches with a vacuum bleeder. It takes me longer to get the tool set up than it does to actually bleed the lines, which I like because it means I’m done a whole lot sooner and can crack that beer early. 
And yes, it is also possible that you got a bad MC -that does happen sometimes.
I didn’t bench bleed either one. How long does it usually take to bleed without bench bleeding? Does gravity bleeding work if there’s that much air in the system? Couldn’t get that to work either, but maybe I’m being too impatient.
This is an old mechanics trick for one person bleeding.
The one thing the video leaves out is, the bleeder screw should be removed and a sealant applied to the threads so air doesn’t get sucked back into the hydraulic system past the threads.
Now you can pump the pedal all you want without letting air into the system.
Just keep your eye on the level in the master cylinder.
Tester