On my '57 88 with manual brakes, I've replaced the shoes on all corners, and I have installed new/rebuilt wheel cylinders and rubber flex hoses. I also have a new master cylinder. No amount of bleeding is resulting in a consistent firm pedal.

The best I was able to get was some pressure after pumping, but the pedal would go the the floor after letting it sit for a minute. I also noticed some fluid leaking by the rubber boot (I think) of the MC onto the floor. I assumed this meant the new MC was bad, but I also saw a note on the MC box that you cannot bottom out the piston in a single MC because the fluid could push beyond the seal and leak. I definitely bottomed it out trying to get some pressure...

I suspect the issue is with the MC since I've bled the lines to each wheel cylinder many times at this point without change. I don't have a vice, so I've attempted to bleed the MC in the vehicle. I have done both the method where you use a kit to route the line from the outlet back to the MC reservoir and the hold the pedal/crack the line method. For now, I've put the old MC back on, but I haven't had a chance to mess with it again. Also, there are no leaks iI can see n the system.

Sorry for the long post - Is there a magic trick I'm missing? I've replace an MC before on another vehicle, and I recall it being a pretty simple process.