YJ power break conversion

[3wheelingCJ]

First I hope that this is in the correct section. Second, I realize that this topic have been beat to near death, but hopefully my question is at least somewhat original.

I just picked up a master cylinder/power booster set up off a YJ. It also came with the combination valve. Currently I have manual breaks with drums all around. I am planning on upgrading to power now and possibly to front discs in the future (not convinced that better braking power in the front is good on the trail).

So, should I keep/reuse the combination valve that came with the YJ setup or just attach the master cylinder to whatever is installed now?

 

[gert]

install the booster only for now. Your master cly has residual pressure valves in it to work with your drums, the YJ only has it for the rear drums provided that it has the same 2 bolt attachment as the YJ master cly. When you upgrade to front disks use the YJ master and and porporting valve

 

[3wheelingCJ]

after looking thru a few write ups on this upgrade I was under the impression that the YJ master cylinder will be swapped in as well.
Not sure if the CJ mc will work with YJ booster.

 

[ThisGuyUKnow]

When i did the YJ swap I used the YJ Master and booster. No other parts from the YJ set up. All I did was bend the factory CJ lines to the correct side and then used adapters to change from the Factory cj threads to the YJ threads. The Cj brake master did not fit onto the YJ booster. Since you have manual brakes currently I'd imagine that even if the bolt pattern matched you couldnt retain your master because isnt there a push rod built into it?

 

[3wheelingCJ]

ThisGuyUKnow,

yes, you are correct, the push rod is built into the cj mc.

What size adapters did you have to get?
Did you have to get an adjustable rob or did you use the one from yj? I've heard that a lot of time an adjustable push rod is needed in order to make the whole set up work right.

 

[tarry99]

after looking thru a few write ups on this upgrade I was under the impression that the YJ master cylinder will be swapped in as well.
Not sure if the CJ mc will work with YJ booster.

It should work as the bolt pattern's are near the same............BUT! One thing on Jeeps is never assume all is the same......
Here is a few things you have to pay close attention too.......the mounting location of your 1975 MC may be in a different location up/down than the later YJ.....which means if the booster is a larger diameter version it may hit the hood. Also did this come with a linkage like adapter that mounts between the firewall and the booster? If not you may need one.

Last........... since you now have manual brakes there is a ratio change on the brake pedal between the manual & power brakes. Meaning the push point or push rod location is different between the two, sometimes the pedals are drilled for both while some are not...........On manual brakes the push rod location is closer to the fulcrum on the pedal set........which gives your foot more mechanical advantage to push the manual system.......on the power system they moved that point down about 1 inch which takes away some of the mechanical advantage since your now using a vacuum booster..........using the manual location with a booster will get you a touchy pedal when you apply the brakes............get your tape measure out and start looking at you system so that you can be prepared.

 

[ThisGuyUKnow]

ThisGuyUKnow,

yes, you are correct, the push rod is built into the cj mc.

What size adapters did you have to get?
Did you have to get an adjustable rob or did you use the one from yj? I've heard that a lot of time an adjustable push rod is needed in order to make the whole set up work right.

go to my ax15 sticky in the drivetrain forum and thumb towards the end, I think I posted the adapters needed in there. I don't remember anymore because I have become obsessed with usihydrobooster setups. I my application I used a yj pedal assembly which is an exact match if you have a powerbooster cj.
tarry is right since in the manual setup the master bolts straight to the fire wall, id doubt tha you would have the same hole centereds between the for books that mount pedal bracket. we may need to see pics of your fire wall and brake pedal.

 

[3wheelingCJ]

I took some pics of the firewall and the break pedal. The pedal pics are not the greatest, but hopefully will show what you are looking for. Let me know if you need more pics.
Looks like there are four holes in the firewall, but I am not sure if the spacing will match. the cable that goes thru one of the holes is choke and I should be able to reroute it, since there is plenty of slack.

 

[3wheelingCJ]

update:
took off the original mc. well, I don't think that it's original since the break lines hook up on the same side as the yj's.
I will have to drill 4 holes in the fire wall in order to mount the YJ booster. The push rod from the YJ is the same length as the one that I took out with a little nudge up at the end, so I think that should work fine.
Now, the break lines that are on now go to the proportional valve installed at the frame. They are also not long enough. So, I wanted to buy two new lines that will be long enough, have the right size adapters and just replace them. The problem that I ran into is the adapters that are screwed into the proportional valve are made out of really soft metal and just keep stripping the edges.
Any suggestions on how to deal with that issue? I ran into the same problem trying to take off the old lines that came with YJ mc, so I just broke them and used a socket. Considering doing the same thing again.
This might be a newb question, but is there a way to extend the lines and change adapters without having to replace them?
Also looking for a good place to connect the vacuum tube to the booster. some people said that they T'd off the EGR valve, but I am not sure if it's a good idea.

 

[ThisGuyUKnow]

update:
took off the original mc. well, I don't think that it's original since the break lines hook up on the same side as the yj's.
I will have to drill 4 holes in the fire wall in order to mount the YJ booster. The push rod from the YJ is the same length as the one that I took out with a little nudge up at the end, so I think that should work fine.
Now, the break lines that are on now go to the proportional valve installed at the frame. They are also not long enough. So, I wanted to buy two new lines that will be long enough, have the right size adapters and just replace them. The problem that I ran into is the adapters that are screwed into the proportional valve are made out of really soft metal and just keep stripping the edges.
Any suggestions on how to deal with that issue? I ran into the same problem trying to take off the old lines that came with YJ mc, so I just broke them and used a socket. Considering doing the same thing again.
This might be a newb question, but is there a way to extend the lines and change adapters without having to replace them?
Also looking for a good place to connect the vacuum tube to the booster. some people said that they T'd off the EGR valve, but I am not sure if it's a good idea.

Your v8 intake manifold should have threaded ports in the intake itself that you can thread in vacuum nipples. I'd have to look but I believe that is where mine was hooked up before I pulled apart everything.

 

[3wheelingCJ]

I talked to a few people and feel comfortable with T'ing off EGR line.
So, in the process I found out that it is a real pain to get break line extensions that also convert from one size fitting to another. Looks like I will be making my own lines once I manage to take the originals off the proportional valve.
Yesterday my break lights were on even when the pedal wasn't pushed. I understand that it's a common issue. Today, I noticed that I forgot to put a little plastic sleeve on the part that goes thru the switch and the push rod. I added that plastic sleeve and now the break lights don't work at all. Any suggestions? I am struggling to understand how the switch operates. I tried ohming it out, but everything is covered in paint and I didn't want to just start scraping it off in case it was that way for a reason.
Also, one of my friends suggested that I check for the check valve in the booster. I don't think it's there. I don't remember seeing it being mentioned in any write ups.