brake issue...

what are some specs info on your jeep? stock running gear? motor?

Cj-

Did you bench bleed the new master cylinder? if you did not a bubble might be trapped. Plus when you do a new master cylinder you should bleed the entire system. Find a buddy and bleed the piss out of it, front and back.
Cj-

Leaking brake power booster can be a issue.. make sure the obvious is good , the vacuum connection.

So when you pump it it gets firmer? Does it stay firm long or fall away. Sounds like your shoes could be out of adjustment.

X2 on the vacuum to the booster, or booster itself...

Sounds too me like the master cylinder has an internal leak. Once your brakes have pressure, if you press the pedal and hold it, does the pedal slowly drop down to the floor?

Double check that you have the steel line going into the wheel cylinder tight enough (it should be dry by now from the previous bleeding). If it is not quite sealed it can aquire an air pocket and or leak fluid and give the symptoms you are describing.

X3 on the brake booster. Check the vacuum line and connections that go from the intake manifold to the booster.

Quote from 1991yj

Ugh. My pedal goes to the floor period haha... there is no pressure on the brakes @ all.... I'm wondering when I changed my rear cylinder if I bled the brakes the wrong way... I was told I gotta bleed all of them starting from the farthest from the master cylinder and work my way around...it started after I did the brake test @ the dmv...

Any chance the master cylinder went dry while bleeding the brakes?

If so, you will have to bleed it first, then the brakes again.

You can get kits to bleed the master for under $10.

It's not going to change the engine RPM... That's like getting an STD from a toilet seat.

Drum brakes suck to work on unless you do it all the time.

Very easy to get stuff back together wrong. I know.

Good idea to pull both wheels/drums, but do one at a time so you can look at the other one.

Happy to say, all my vehicle wheels have discs. ;D

Did you check to see if one of the metal brake lines isn't leaking? Maybe when they did the brake test a line blew out? Oh in my over 20 years of work in a automotive shop i've never once seen a self adjuster that didn't need to be manually adjusted.

Sounds like you need to do a full bleed on the system making sure the MC stays full. Did you install the new rear drum brake cylinder with the bleeder valve facing the right way? is sounds like the MC drained while you were changing the brakes, or there could be some crud in the system. I would pull the MC, clean it, bench bleed it, and then bleed the entire system.
It sounds like you have a bubble somewhere.

Cj-