Here is the whole 14 month brake story during the restoration of my jeep. 

                The PO had switched the front over to the K10 front disks. 

The parts he used: (according to his paperwork he gave me)
Caliper mounting brackets from the wrecking yard - '81 Chevy 1/2 ton 4WD (K10).
Caliper - '71-'78 Chevy K10 - Oreillys Part #: 18-4046 Left
Caliper - '71-'78 Chevy K10 - Oreillys Part #: 18-4045 Right

The PO left the single stage master cylinder in place and put a remote reservoir made of 3 inch PVC pipe on the firewall with a hose running to the lid of the original master cylinder.  It worked but would not look to good on the restoration.

So as I started the restoration process, I thought it would be best to replace the master cylinder to something better and with no remote reservoir on it.  I opted to go with a dual reservoir that fit a 80’s Ford Fairmont. (Someone else on the CJ2A page had used one, so I figured why not.)   

I made a mount and had time to fit it all in place because the tub was off and it was easy to put the new bracket in place. 

The first master cylinder was a cast iron rebuild and it would not put out any fluid to the rear brakes at all.  Defect it out and put in an aluminum rebuild.  The aluminum one would never build any kind of a pedal, so back it went and I bought a brand new cast iron master cylinder.  Put that in and again had problems, no fluid to the back issue. I also believed that it must have had residual valves built into the master cylinder ports.   I moved the moved the master cylinder forward as far as possible and re-manufactured the brake push rod, it needed shortened. I moved the master cylinder back and forth until I had about 2 to 2 ½ inches of rod movement on the master cylinder piston.   

I plumbed it this way….

From the master cylinder I ran the brakes lines first to a residual valve before the proportion valve.  So it goes back outlet of the master cylinder to the input of the 2 pound residual valve.  The outlet of the 2 pound valve goes to the input of the proportion valve inlet which is on the top of the proportion valve.  (this is for the front brakes)  So the front outlet of the master cylinder goes to the 10 pound residual valve inlet.  10 pound outlet goes to the proportion valve on the top side. (this is for the back brakes)  This proportion valve also has a brake light switch put in it with a wire loom.  From the proportion front output (one is plugged off) it goes to the rubber hose near the front driver’s side.  The proportion valve last output goes to the rear brakes hose from above the rear end. 

After doing all of this, the brakes still did not work, so I started to take parts out one at a time.  Starting with the front residual valve, but I would still have both brake caliper hang on me and both of the front brakes would start to stop the jeep going down the road some times.  The next time you would drive it not a problem and everything worked fine.  Next I tried taking out both residual valves and still no back brakes and the front would still gradually get hot and stop the front rotors.  Next I took out the proportion valve, no change.  Finally it I was down to just master cylinder, lines and brakes, still no back brakes at all.  With no back brake and the front brakes not releasing and brake drag…..I about started to pull my hair out finally after talking with my dad, who worked as a mechanic for many years  back a few days, we came to the same conclusion, the master cylinder I was using was not putting enough fluid to the back brakes and the fronts would not release enough.

 I hit the computer again and started to dig.  I ended up finding on the early cj5 page, a swap someone had done using the same parts as the PO did on my jeep.  I took the time to call Doorman and talked with a tech support guy.  He pulled up the drawing and said that this cylinder did not have any type of residual valve at all.  Bingo, I hit pay dirt and started to put it all back together again. I did have to shorten the two banjo bolts about 1/4 of an inch to get them to both tighten down tight.  I just used a small angle grinder with a sanding pad on it.  It took about 5 minutes each and a few trial fits to make sure it all would fit.  I also had to grind a small amount off of the engine block to ensure clearance between it and the master cylinder banjo bolts. I took off less that 1/8 of an inch.  I returned all of the other parts into my system as well, being both residual valves and the proportion valve.  Again I bleed the brakes only to find that the fittings I had were leaking, so out it came again.  More research and a small amount of sealer on the pipe threads, notice I said pipe threads and not inverted flare threads.  It all works, I need to adjust the push rod to get just a little more brake pedal but I truly believe we have finally beat the no/barely working brakes!

Here is the list of parts and the vendors I used

Doorman M56193 New master cylinder to fit 1972 jeep cj5 with drum brakes Amazon

Two Fragola part #650156 Banjo Bolts Jegs (phone them this is not a stocked part)  It comes with two washer seals but they were the wrong size, too big so I got something else.

Four copper brake line washers ½ diameter from the parts store.

Two (E-10-8) Inline Tube 90 Degree Brass Elbow with Male 1/8" NPT Pipe Thread and Female 3/8"-24 Inverted Flare for 3/16" Brake Line Amazon

Permatex #59235 high temp and for hydraulics   local parts house

Brake line I made all of my own

One (E-6-6) Adjustable Proportioning Valve Distribution Block Disc Drum Brake Street Rod BLK Amazon

One set of Pirate Mfg Residual Valve Disc Drum Brake Set Check Valve Hot Street Custom Rod 2 & 10 LB  Amazon

This seems really short for all the problems I had getting these brakes to work but here it is.