I'll start by answering your question about the size of the rear brake line vs the front. The reason the rear brake line is larger is because it's a single line going back from the prop valve to a t-fitting on the rear axle. Both front brakes are fed from separate lines all the way from the prop valve to the calipers, so they can be a little smaller diameter.

Ok, so the best and easiest way to bleed brakes IMO, and you are going to receive alot of opinions on here, is to pressure bleed. I use a bug sprayer and a plate I c-clamp to the master cylinder with an old seal. You can buy a real pressure bleeder too.

Sometimes even with pressure bleeding I have a hard time getting brakes bled. So what I do in that case is put good pressure on the master cylinder, crack a bleed nipple. Alot of times there's no fluid. I just leave it cracked open a little. While that is happening I go over and work the heck out of the brake peddle like 20 times, or till I get fluid flow. At that point it bleeds without working the brake peddle anymore. Sometimes the prop valve causes complications and that's how I get past them.

The pressure bleeder also finds any leaks for you right away without even having the apply the brakes.

 

No mention of centering the safety valve built into the combination valve ('Proportioning' valve).
Without centering the valve & holding it in place it will cut off one end or the other, there is a tool for that very job, or one can be made easily.

 

I specifically omitted talk of the centering valve in my reply. I've lost count of how many CJ brake systems I've pressure bled and never had to waste a moment messing with that little valve. I guess I'm just lucky.

 

you can get lucky 90% of the time, it may just be non operational. But occassionaly it shuts off due to the differential pressure, which you would expect f you have full pressure on one side only and the other is open.

Fortunately a simple thing to check and correct.

 

People don't post 'Help Me' threads when the job is a breeze and everything goes right....

I don't need a valve clip in 39 out of 40 jobs, the 40th gives me fits and I have to figure out why.
Old valves seem to have a bigger issue with double diaphragm conversions, I would assume it's the extra pressure pushing the piston into built up crud areas it didn't normally travel into, but that is just a guess from seeing the rust, corrosion, crud in the valve once I took them apart.

Just an idea for the guy having issues, something I've run into a few times.

 

I used to dread having to bleed brakes. It always used to be a task full of frustration. Never went well. Well that is up till I started pressure bleeding. My only point is try pressure bleeding. OP you'll never go back once you do

 

Work you way from the PV to the wheel. Start by disconnection the line for the PF at the PV and slowly press down the pedal and check for fluid. If you do, then move the the next connection and slowly pump until/if you have fluid there. Then next and so on. This will let you know where the blockage is.

 

So only one line on the front doesn't work on the front?

And when you blow the front line out with an air gun from the MC both front brakes blew clear?

Hmm...
That all most rules out the Combination valve. At least the safety valve is working. But there could be a piece of junk blocking the outlet by the metering valve.

Do you have solid pressure on the pedal with all lines closed? Does it creep down?
Do you have solid pressure on the pedal with 3 good lines closed? Does it creep down?

I'd still do what Fourtrail suggest and open up each connection one at a time to verify fluid flow.
Protect your eyes that it doesn't spray out unexpectedly. Painful stuff...

I have been blessed that my brakes work good enough I can just gravity bleed the brakes.

 

If you are using a suction bleeder, make sure that you have the pedal pushed down far enough that the ports in the master cylinder are open. If you pull a vacuum on the brake system, there is a chance you will boil the fluid, introducing more air bubbles into the system.

I see that the OP had a pretty decent vacuum pulled and then the pedal was pushed, def a blockage somewhere as that would have pushed a large volume of fluid to the caliper.

Also, doesn't seem to be the issue with the OP's used calipers, but talking with the counter guy at my FLAPS, he mentioned they have gotten a few rebuilt calipers that when they filled/tapped/drilled the inlet fitting to fix it, they didn't drill far enough to get into the main body of the caliper and he got no fluid flow to the bleeder.

 

I am not sure you need to press the pedal down. It is a very common practice to gravity bleed a brake system. I think once the pedal is depressed, the pressure side of the system is cut off from the reservoir otherwise the pistons would squirt fluid into the reservoir rather than the brake line. I know at the beginning of the stroke, the fluid will shoot up into the reservoir if it is not filled up enough, but I think this is only at the beginning of the stroke.

 

Thanks Fellas.....here are my thoughts.....

I am very much trying to avoid disconnecting the lines at the PV. Besides the exhaust blocking it, I have the automatic linkage that is attached and it takes a good amount of time to get in there and there is not way I can remove the lines without removing the PV. It just a royal pain and if I can avoid that I will give all other options a go first before taking it all apart again. My logic is that all three lines (both rear and front left) are free and clear. I had not thought of the PV not being centered - so thanks for that info. I took that boot off of the metering system shown in John Stenks image and I can press the center "button" - it moves about a mm...is that normal? I then went over to the bleeder and put ~25#'s of suction while holding in the button with no luck. So I am hesitant in building a tool to hold it unless it really needs to travel much deeper in. Also - When I originally removed the
PV I did not remove the metering assembly. I just used brake clean in the ports and blew it out with compressed air. Should I remove the metering piston while installed on the frame rail and see if there is something in there blocking the port?

Lastly, to the comments about a pressure bleeding system - Would really like to get this going with the existing tools I have but will consider it I continue to fail at this

 

I know brake fluid is powerful stuff but is Brake Clean safe to use on the rubber parts inside the combination valve?

 

I see replacement proportioning valves ranging from $50 to over $100. Any suggestions...obviously want a good quality part

 

I bought an adjustable PV made by Wildwood...my CJ5 is very lightweight and the rear drums would lock up too easily. It was quick and easy to dial it in.

And...I had the same problems bleeding my lines as you're having now!

 

Ib saw the adjustable version...that's just the the rears right? If so, how did you connect the front brake lines together?

 

You can get this adjustable setup that includes the bracket and the lines that just bolts up.

https://www.summitracing.com/parts/clp-pvksapvdb/overview/

The valve has two ports in the valve for left and right front brakes.

In my installation, getting the frame mounted valve away from the headers was a required upgrade. The header was wearing a slot in the brass valve that was mounted to the frame and I assume that the valve was cooked by how poorly the brakes worked when I purchased the Jeep.

 

......

In my installation, getting the frame mounted valve away from the headers was a required upgrade. The header was wearing a slot in the brass valve that was mounted to the frame and I assume that the valve was cooked by how poorly the brakes worked when I purchased the Jeep.

That really is the worst spot to mount the valve. I kinda like the YJ setup were the valve is mounted under the Master cylinder.

I made a heat shield for mine with a piece of sheet metal. I held it in place with the two bolts and a couple of washers to space it off. After spending all that money on preformed tubes, I didn't want to change it.

I wonder if you CJ-7 guys could just order a YJ set of brake lines and mount it like the YJ's have it.

 

Wanted to touch base and close this out. I am fixed and am a little embarrassed .... I found and replaced the proportioning valve thinking that was somehow the problem and that it was the ONLY part that I had not replaced. Replaced the PV with one from in line tube which was almost 100% match except for the adapter to the rear line and the 2 wire vs the stock 1 wire. The problem still was present after the PV install. Still no fluid at the front right wheel. Started taking lines off and found that the Crown Performance custom made flexible line was not manufactured correctly and material remained blocking the hole where the banjo bolts installs. A dental pick and I removed the blockage and everything worked out great. However, my experience with Quadratec was not so wonderful. I tried to give them an earful, but could not get through to their customer service department for days. When I finally spoke with them via email - they admitted they dont staff their customer service department as much as they do their ordering department. UGH - I called them 6 times and was on hold up to 30 minutes each time...wtf?! Anyway, they could care less that the line was defective even though I explained that this is a critical brake component and probably should have a bit better quality control especially since its a custom made to order product. I wont be doing business with them anytime soon. I was pretty disappointed and have spent thousands with them over the years on my two classic jeeps. HOWEVER, I was very impressed with the dual diaphragm booster I had made for me from Off Again 4X4. Their unit fit perfect and the M/C lined up to the stock hard brake lines. It even fit with out modification with the motorcraft 2150 carb. AND, its can lock up all 4 tires which are 33's. So I am happy with this upgrade. BTW, its the only dual diaphragm booster I could find that clearly fit with the motorcraft. I bought a booster/MC combo off of ebay and back it went because it clearly would not fit and I was not willing to do extensive mods to make it work.

The only oddity in this whole mess is that my brake light does not turn on when I start the jeep - I realized that it has never turned on except when I have the parking brake on. I tried to chase it down, but I could not figure it out since one part of the circuit wiring goes into the steering column to the ignition switch. Maybe a bad switch?