Step by Step Brake Master Cylinder Install/Replacement - Manual Brakes - 75' CJ5 - JeepForum.com
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post #1 of 6 Old 05-24-2020, 06:45 AM Thread Starter
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Step by Step Brake Master Cylinder Install/Replacement - Manual Brakes - 75' CJ5

I installed a new master cylinder in my CJ5 yesterday and it went really well. Being my first time messing with a brake master cylinder, I had a lot of questions about my specific scenario going into it, and had a hard time finding the answers I needed so I figured I would write this up in case it helps someone else down the road. This community has helped me immensely; hopefully this helps someone else out down the road. I am no expert, but I do my research and I do my best to do things the right way the first time. Feel free to let me know if you disagree with my approach on any of this or if anything I stated is not accurate. This is what worked for well me.

My jeep is a 1975 CJ5 w/ a 304 the original, manual (non-power) drum brakes. I have 11" drum brakes all around which I have recently completely rebuilt.

My symptoms were I started getting really spongy braking recently, where the pedal would sometimes hold pressure and other times it would want to go to the floor. Additionally, if you held pressure on the pedal it would slowly lose that pressure over time. I first bled my brakes really well (gravity bleed style) but that had no effect. After reading up about brake master cylinders I concluded that was my probably my issue. I had been having brakes issues for awhile and was doing a lot of pumping my brakes to account for it (during my post MC install adjustments, I found the source of my other problems - a spring was missing in one of the rear drums which I'll talk about later), and somehow that additional wear and tear caused damage to the master cylinder. Or maybe it was just time for it go. Regardless, the new MC made a HUGE improvement and as long as the new part lasts I will be really happy with the result.

The biggest question I had going into this, and where I found the most confusing answers online, was about whether or not I would be able to use existing actuating link/pushrod, or if I should use the one that came with the new MC. This ended up being a non-issue because the new one did NOT come with an actuating link. The 1975 TSM says that the existing actuating link MUST be used, so that is what I did, but I had no choice - the Raybestos unit does not come with one. The instructions for jeeps with Power Brakes are different than below so it is important to make sure you get the correct MC. I believe folks with Power brakes will have a MC that uses a shorter pushrod and they do not need to disconnect the actuating link from the brake pedal since they mount right up to the brake booster instead.

Note: The install instructions below are for manual brakes only.

Parts/Tools:
Master Cylinder: I like to use RockAuto as a starting point for finding parts because I really like their layout for finding things specific to your year, model, and engine. I checked what they had listed for a 75 and landed on the new (not-reman) Raybestos MC. Part #: MC36237
https://www.rockauto.com/en/moreinfo...9474&jsn=12734

MC Bleeding Tool: I also picked up this master cylinder bleeding tool made by Cardone. I can't speak to whether or not it is truly easier than using a normal MC bleeding kit with the tubes, but I really liked how this worked and found it super easy. After just a couple of pumps all the air was removed and the MC was ready for install.
https://www1.rockauto.com/en/moreinf...=3744840&jsn=4

Flare Nut Wrench: I recommend using a flare nut wrench on your brake line fittings. The extra grip the fittings will ensure you don't strip them and end up having to replace an entire brake line so to replace a fitting. I picked up this really cheap set awhile back, and the are really solid.
https://www.amazon.com/Crescent-CFNW...xpY2s9dHJ1ZQ==

Snap Ring Pliers - Right angle would be best if you have them but I was able to do it with straight ones

Step by Step Install:
- Put a towel below existing Master Cylinder to catch any spilled brake fluid and protect your painted surfaces - brake fluid will EAT your paint
- Loosen Master Cylinder bolts at the firewall but do not remove yet
- Disconnect stoplight switch and actuating link from brake pedal
- Disconnect stoplight switch from brake model linkage. You'll need to removing cotter pin first, and then try and move the brake pedal over the right to the switch off. The switch has a closed circle side and a half open circle side. Depending on how your switch was installed you will either need to pull it up or down to get it off - I had to get my full circle side off first and then pull down. You can't see the half circle side in the photo I included, it'll be towards the passenger side.
- Disconnect Actuating link from Brake Pedal by pulling brake to the right and link to the left - mine came off fairly easily with some wiggling
- Remove Brake lines from MC - fittings are 9/16" and I used the 9/16" flare nut wrench
- Remove MC flange mount nuts and pull the entire thing away from the firewall. The actuating link with come through the whole and the whole thing will come out as one.
- Remove actuating link from old MC so you can install it on the new one
- Pull back the rubber dust boot from the MC to expose the snap ring
- Using Snap Ring Pliers remove the snap ring; the actuating link will pull out of the MC now - catch and save all the pieces for now
- BE CAREFUL HERE - my new MC did NOT come with the Wire Clip shown in the diagram and this part will be needed when you install the actuating link on the new MC - I took this off last as explained below
- Carefully pry off the retainer with needle nose pliers and remove the washer and snap ring from the link
- (only needed if your MC didn't come with the wire clip) Use a flat head screw driver with a fine tip, or some other suitable tool, to careful remove the wireclip - I worked it up out of the groove slowly and then slip it off so I could re-install it later
- Clean the actuating link - I used cheese cloth to polish it up as best I could as it had some light pitting
- Remove Snap Ring, washer and retainer from NEW MC being careful not to damage anything
- IN THIS ORDER - install the parts you took off the NEW MC onto the old MC actuating link as shown in the diagram from the non-eye side of the link - New Dust Boot (small hole goes towards the eye of the link), Snap ring, Flat Washer, Retainer slides up into the cut groove (pay attention to orientation as this part could be easily damaged and difficult to remove), and then finally slide the wire clip up into the groove below the retainer
- Install link with new parts onto new MC - this can be tricky - push it in slowly, hold it down, and use your snap ring pliers to set the snap ring making sure it is fully seated
- Secure dust boot to the end of the MC
- Bench Bleed new MC
- NOTE: this is what worked for me. There are multiple ways you can bleed the MC so do what you feel comfortable with, just make sure you do it
- Wear safety googles to make sure you don't get brake fluid in your eye
- Mount your new MC in a vise by the mounting flange and get it 100% level front to back, side to side - this is really important to make sure it is bled correctly
- Fill with new dot 3 brake fluid to at least half way
- Using the Cardone tool, you carefully suck fluid out of the Resovoir, remove air bubbles by pointing it up and squeezing it until only brake fluid comes out the tip, and then push it firmly against one of the brake line ports and push it back into the MC. You will see lots of air come out until eventually a steady stream of liquid. I did both sides multiple times to be sure, but always make sure there is fluid in the resovoirs
- Fill the reservoirs with fresh fluid to approx. 1/4" from the top and secure the cover
- Install new MC on the firewall loosely, pushing the actuating link through the firewall
- Reconnect actuating link to the brake pedal, and the re-install your stoplight switch and cotter pin
- Tighten MC flange nuts and secure it to the firewall
- Reconnect your brake lines to the MC
- Bleed your brakes to make sure you get any remaining air out of the system
- I prefer gravity bleeding as it is easy with one person, works really really well, and pushing the brake pedal to the floor isn't a great practice for the health of the MC
- Grab a beer, she's done.

Original MC




Actuating link and stop light switch removal



Removed actuating link from old MC before install new parts - new parts will go on in same order and orientation



TSM showing correct order of parts for actuating link - see where my finger is pointing





Bench bleeding new MC



New MC installed



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post #2 of 6 Old 05-25-2020, 04:11 AM
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A tool i recently picked up was a vacuum bleeeder. works off a compressor. bleeding is now 2 minutes.

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post #3 of 6 Old 05-25-2020, 11:08 AM
hbar
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Quote:
Originally Posted by PottsyCJ5 View Post
- Install new MC on the firewall loosely, pushing the actuating link through the firewall
- Reconnect actuating link to the brake pedal, and the re-install your stoplight switch and cotter pin
- Tighten MC flange nuts and secure it to the firewall
This is the most fun part of the job if you're doing it by yourself. One hand holding the MC, the other hand reached up under the dash trying to blindly get the nuts seated & tightened enough so that the MC won't tip & spill brake fluid all over everything.

Also fun: trying to decide if your new MC won't bench bleed because you're a rookie and have no idea what you're doing or if it's because you bought remanufactured Chinese crap. (In my case it was the latter)
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post #4 of 6 Old 05-25-2020, 12:06 PM
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hello

first wanted to say nice write up of changing the MC. i also gravity for alot but then i also pressure bleed. i bought a pressure bleeder for doing all my vehicles. here is a pic of the bleeder that i use.
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post #5 of 6 Old 05-26-2020, 11:01 AM Thread Starter
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Quote:
Originally Posted by hbar View Post
This is the most fun part of the job if you're doing it by yourself. One hand holding the MC, the other hand reached up under the dash trying to blindly get the nuts seated & tightened enough so that the MC won't tip & spill brake fluid all over everything.

Also fun: trying to decide if your new MC won't bench bleed because you're a rookie and have no idea what you're doing or if it's because you bought remanufactured Chinese crap. (In my case it was the latter)

Yeah, that part is not fun but wasn't too bad - I was able to reach the back of the bolts and keep my hand on the flange nuts. For me getting the brake light switch back on was the bigger pain though. That thing is annoying and the space is limited. You have to have everything positioned just right, and on my brake pedal there was a white bushing that kept getting in the way.

I'm pretty sure the the Raybestos MC I bought was built in the USA which I appreciate. Seems like a well built unit.
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post #6 of 6 Old 05-26-2020, 11:10 AM Thread Starter
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Step by Step Brake Master Cylinder Install/Replacement - Manual Brakes - 75' CJ5

Ive never seen a set like that oldshcool. I will have to check it out. I really don't like needing a second person (usually having to ask my wife) to pump the brakes, and I don't think shoving the pedal to the floor is good for the MC seals either.



I have a MityVac vacuum bleeder but it takes forever if you have a decent amount of air in the lines. I stopped using it and only use that for vacuum tests and other things now.



Once I started gravity bleeding, and I got ALL the air out, I get a nice steady stream of fluid coming right out as soon as I crack the lines. A pressure setup like yours would have made things a lot faster though. Gravity bleeding can take a long time if you have a lot of air in the lines, but it does work and the materials needed to do it are probably already in your garage and can be done alone: a clear tube that will fit securely over the bleeder screw and a jar with a lid. Cant beat that in terms of cost.



Quote:
Originally Posted by oldschool74cj5 View Post
hello



first wanted to say nice write up of changing the MC. i also gravity for alot but then i also pressure bleed. i bought a pressure bleeder for doing all my vehicles. here is a pic of the bleeder that i use.
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