Rear master bleed problem (Think with me)

[Gramatron]

Hey guys,
So I had to acquire a rear master for my bike a while ago. I bought all new hardware for it too. I'm reading that these guys are a bear to bleed when they're dry. But I want to see if I'm missing the problem with this one.

The metal plate had a little rust going on but I didn't see it anywhere else in the internals. The rubber piston head looked healthy and fluid had reached it.
Frequent flapping of the brake pedal yielded some bubbles, but after hooking up a vacuum bleeder, the fluid level didn't change and there are no more bubbles.
I've eliminated the brake line as the source of the problem and adjusted the actuator rod to rest firmly against the piston.

Do I just need to stay the course here or am I missing something?

 

[Slojza]

Is the cap sealing well? I had this problem that the cap was not sealing well so there was no pressure, but the piston (although still original) worked well so it was "bubling" when opened. Hope it´s not your case cause the rubber seal is discontinued and hard to find.

 

[Gramatron]

Hmmm. I figured that the cap should be off while bleeding so I don't have a vacuum in the wrong place which would prevent flow into the line. Everything is dry at the moment.
I believe my seal is good though.

 

[Slojza]

I believe the cap must be on while bleeding. At least i couldn´t make it work any other way

 

[Gramatron]

I just realized I never closed out this thread. Problem Solved.

I completely disassembled the master and on a friends advice blew it out the body with a compressor and air gun. Something had gotten lodged in the works and that seemed to clear it out. After I reassembled it, it bled readily.