I've done quite a bit of research and think I've narrowed it down to the combination/proportioning valve. I've never messed with these things before but here's what I've gathered...
The valve allows brake fluid pressure to flow to the front and the rear. If it senses too much flow to one or the other, it will close off that side as it sees it as a potential leak. The purpose for this is to allow you to still have [some] brakes if a line were to burst. When this happens, assuming everything is working, your brake light will come on. Last night I verified that my brake light is now on. Since I have no pressure to the front, I'm assuming the switch triggered to shut off the front.
My solution?
I bought some short brake lines and fittings. I'm going to pull the master cylinder and bench bleed it the proper way to ensure all of the following work is not a waste of time.
Next step - If you don't have the special tool used to keep the valve/switch/pain in the *** yet awesome safety feature in place, there are a couple options. I've read that an 8 penny nail with a rounded off tip is the same diameter as the switch plunger. Poking that around in the hole may reset it. I'll consider this method.
The other method seems like it could be more fun. I've read that if you pump up the brakes and really mash them down while cracking open a bleeder valve on the working side of the system, the valve will reset. Hopefully anyone trying this will wear safety goggles. I sure will!
Either way, if you're brake light is functioning as it should, you'll know the valve reset if the light goes off.
Once the valve is reset, if you have the tool to hold it in place, you're set. Bleed the brakes as normal. I've always heard to bleed from the furthest bleeder from the master cylinder to the closest bleeder to the master cylinder:
Right Rear
Left Rear
Right Front
Left Front
Now, the factory service manual from 1976 states to bleed as such:
Left Front
Right Front
Left Rear
Right Rear
This doesn't make sense to me but then again, I'm no master technician. My advice would be to pick your favorite method and give it a try.
OK - That seems easy except for the part where I don't have the tool nor care to buy one. Instead, I'm going to be difficult.
Let's assume the valve has been reset and we're ready to bleed the brakes. Here's what I've read on how to bleed the brakes, including how to fill dry lines, without popping the valve.
GENTLY bleed one front wheel, then one rear wheel. Repeat until you have fluid at all 4 wheels. Once fluid is at all 4 wheels, the valve should have enough compression to allow you to gently bleed all 4 wheels in the proper order. For me, I'll bleed from the furthest wheel to the closest:
Right Rear
Left Rear
Right Front
Left Front
I'm not sure when I'll get a chance to go at it again. I'd like to do it this evening or at least before Friday but we all know how busy life can get, especially with a wife and a 1 year old. Either way, I should know what's what by the end of the weekend (or earlier hopefully). That being said, I'll continue to research and will update this thread with any news. If anyone has any information, please don't hesitate to chime in!
Sources:
(Hopefully I can link another forum here. If not, my apologies!)
http://www.jeepforum.com/forum/f8/brake ... d-1797153/
8 Penny Nail 'Tool':
http://www.jeepforum.com/forum/f8/brake ... st18246162
1976 FSM on Brakes:
http://oljeep.com/gw/76_tsm/Section9.pdf