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CJ to YJ Brake Booster Conversion

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Posted 08 August 2007 - 05:32 PM

CJ to yJ Brake Booster Conversion



A lot of people put large tires on their Jeeps, winches, tire carriers etc etc. With all that extra weight what people often overlook is upgrading the means by which you stop all that stuff when going down the highway or a steep grade on the trail. The braking system is one of the most important parts of your jeep, so it is imperative that this system is addressed once you've increased the vehicle weight in order to stay safe.

There are of course several options you have once you decide that is it time to upgrade. Prices can range up into the hundreds of dollars for hydro boost setups, or full units, such as the one from Navajo, which runs close to $400. Other options include trips to the junkyard to pull a unit from some other vehicle and "adapt" it to work in your CJ. I've heard of people using brake boosters from Cadillac's, Chevy trucks, as well as others. Although I have no personal experiences with these, I'm sure all of these could work, in some form or another. However, chose the YJ setup for several reasons.



Cost - Prices vary, but for example, at your local "Junk yard" you can grab a YJ master cylinder, booster, and firewall bracket for about $20.00. Add the cost of some brake fluid, and a few brake link unions, and you can do the entire upgrade for less then aprox $30.00 There are cases where the pedal is soft or spongy after this install. It's caused by the length of the push rod being too short. It is recommended you purchase an adjustable brake push-rod from www.tricountygear.com or www.mopartsracing.com
It is not necessary to use the YJ proportioning valve.


Ease of Install - I would guess that the average install time for this modification is about 2-3 hours for someone who has never done this before. It is very close to "plug and play" as you'll see in the step-by-step below. It does not require any special tools.


Parts Availability - All parts used in this upgrade can be purchased at your regular run of the mill parts store with the possible exception of the brake unions.

For CJ owners running the stock manual brakes, this upgrade is like night and day. Additionally, as compared to the CJ power brake setup, there is a noticeable difference.

Note: Check that all other components such as calipers, brake cylinders, etc., are in perfect working condition on the vehicle at the time of the install.


Parts List

1987-1995 Jeep YJ(Wrangler) Master Cylinder, Booster, Firewall Bracket
You can normally grab this entire unit all bolted together out of your local junk yard.)
3/8" threaded-1/2" NPT brass fitting
3/8" Regular Vacuum line
You only need this if you could not grab the vacuum line off of the YJ when you got the Booster.
Brake Line Adapters/Unions
(1) Weather head Part # 7917
(1) Weather head Part # 7912
These are available at Napa.
Brake Fluid

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Tools List
Standard Socket Set
Needle Nose Pliers
9/16th drill bit optional
Self Bleeder Kit optional



Install


Step 1 - Remove the old master cylinder

If you're running the stock carter carb , I would probably take the housing off and put it to the side so you have room to work.

A. First thing you do is remove the cotter pin that holds the brake rod to the pedal. You'll need to get under the dash, and look above the steering column to find this. Needle nose pliers work well in pulling it out. Save this pin as you will need it to install the new master cylinder. If it breaks, they can be purchased at your local parts store. I recomend a new one for the install.

B. Once you've removed the cotter pin, you can go back into the engine compartment and remove the 2 brake lines from the master cylinder. A flare nut wrench works well for this.

C. Now go ahead and remove the 2 bolts* that hold the master cylinder onto the firewall. These bolts are 9/16th. You may need another person to hold the nuts that are on the inside of the firewall while you back the bolts out.
* If you're currently running manual brakes, there are 2 bolts holding the master cylinder in. If you have power brakes then there are 4. You will use these same 4 holes for the new setup. I've seen some jeeps that have the 4 holes drilled, even though they have manual brakes, and some that do not. So, some people may need to drill those 4 holes out for the new master cylinder.

D. Once the 2 bolts are out you can completely remove the rod from the brake pedal and take the master cylinder all the way out.

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Step 2 - Install the new YJ master cylinder

A. Hold the new master cylinder up to the firewall in the same spot the old one was, and bolt it in. As mentioned before, if you're converting from manual brakes, you may have to drill the 4 holes into the firewall.

B. Reconnect the brake rod to the pedal assembly and put the cotter pin back in the rod. Now your new master cylinder is attached, and its time to install the brake lines.

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Step 3 - Attaching brake lines

A. Take your new brake line unions and screw them into the YJ MC. Make sure they're tight.

B. First thing you'll notice is that the YJ MC has the threaded holes for the brake lines on the opposite side as the CJ MC. There are several ways to address this, simply bend the lines around to the other side, while keeping several of the loops in the old brake lines in tact. Be sure to leave enough clearance for the throttle linkage on the carb. You want to make sure that nothing will rub on the brake lines under any circumstances. Be careful bending the lines so as not to put any kinks in it. A brake line bender may come in handy.


Note: This setup is utilizing the CJ proportioning valve in its stock location on the frame rail as well as all current brake lines.
Step 3 - Attaching Vacuum Line

When you grabbed your YJ system from the junkyard you may or may have not grabbed the vacuum line that runs from the brake booster. I'd suggest you do. But if it is not available then just go to the parts store, and get about 12" of regular 3/8" Vacuum line. You'll also need the brass adapter mentioned above.
The booster needs a vacuum source to operate correctly. You can really use any source you wish. What I do is use the one above the EGR valve as seen listed below.

Take the end of it off, (it is a 3/8" bolt) and replace it with the threaded end of your brass fitting. Then you can attach the line and run it up to your booster. Its as easy as that. This pic shows and optional vacuum source for the booster..

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Step 4 - Bleeding your brakes

Now it's time to get the air out of your newly improved system. I'll assume you already know how to bleed brakes. Start with the wheel furthest from the MC and work your way closer. This means the rear passenger side wheel, then the rear drivers side, passenger front, and finally drivers side front. You may have to go around a few times to get all of the air out. Don't forget to bench bleed your MC if you have a new one. I have not done this on units I've pulled from the yard and I've never had any issues.

Bleed the brakes.


Notes:

1.Brake lights on all the time?
The YJ booster red is roughly 1/4" longer then the CJ rod. In some cases, we've had an issues where the brake lights would be on all the time because the brake pedal would not make contact with the switch which turns the light off. What you can do is bend the tab on the brake pedal slightly, and then it makes contact. Problem fixed.

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2. Does the pedal feel soft?
This could be a combination of things. First re-bleed the brakes several more times. This is probably the main cause of a soft pedal. Also, make sure you have no leaks, and check your self adjusters in your rear brake drums. Sometimes these need adjustment. This is done by simply jacking the vehicle up and turning the little cog wheels inside your drums with a flat head screw driver. If re-bleeding doesn't help, refer to the beginning of this writeup for the adjustable push-rod.

3. Which Proportioning Valve should I use?
The answer is either one. They seem to be identical with the exception of where they are located. In the above application the stock CJ prop valve was used.


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#2 User is offline   Rollbar 

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Posted 22 November 2007 - 02:19 PM

Here is a web site that sells the complete kit, just bleed & install.

Vanco Power Brake Supply
*MY CJ IS YOUR yJ's DADDY*

*Who Needs A Stinking Manual When You Have A Fat Wallet For Tech Support!*

*What man is a man who does not make the world better*

Support the Central Florida Bible Camp for kids

'65 CJ5 Navy; '74 CJ5; '80 CJ7; '84 CJ8; '86 CJ7
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