Jeep JK J8 master cylinder and booster installation - including what not to do
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- Опубликовано: 5 авг 2024
- Here's the installation video of the military spec Jeep J8 master cylinder and booster (Mopar Performance part number P5160050) in an automatic 2012 Jeep Wrangler JKU.
Unfortunately I mucked up part of the install (documented to spare you) and damaged the master cylinder. I found a Crown Automotive 68048757AA master cylinder had a quicker availability than the Mopar part (which is more expensive as a single item vs the above mentioned complete kit).
Parts included in this kit:
- 68048755AA - Booster
- 68048757AA - Master Cylinder
- 68048758AA - Reservoir
Hope the steps in this video help you avoid the same mishap.
This upgrade works beautifully with the following brake upgrades:
- Mopar JL HD brakes kit: • Installing Mopar JL HD...
- Parking brake tensioner fix: • Jeep Wrangler JK/JKU p...
00:00 Intro
00:29 Disconnecting brake pedal
02:50 Removal of stock master cylinder
03:49 Empty reservoir
04:57 Unplugging connectors
05:57 Removal of stock booster
07:23 Remove booster
08:54 Move booster to bracket
09:44 Installation of Mopar J8 booster
11:03 Test fit of J8 master cylinder
12:17 Mopar master cylinder bench bleed
13:01 Damaging Mopar J8 master cylinder
16:12 Inspecting the damaged master cylinder
16:47 Comparing Crown to Mopar MCs
18:07 Crown master cylinder bench bleed
20:31 Installation of Crown J8 master cylinder
25:28 Brake bleed
25:50 Conclusion 
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Just installed this set up on 2016 JK with the Tera Flex Delta brake kit. This video helped prepare me, I thank you. I would like to add, for my application I have about 35 wires running through the little hole on the booster mounting plate. For those like me who do not want to cut and splice all those wires when removing the booster, I first removed the master cylinder, then I was able to remove the four mounting nuts that secure the booster and bracket to the fire wall, then I was able to slide the booster and mounting bracket far enough away from the firewall to access the inside four nuts securing the booster to the bracket. So no wires had to be cut or rerouted. Also, thankfully the brake pedal clip came off easy enough with zero damage. Oddly enough I did not need to move any other components out of the way, everything wiggled in good to go. Thank you again and sorry for your troubles.
I believe that hole is where the clutch master cylinder is routed through the firewall for manual tranys. Brothers with automatics tend to rout accessary wiring harnesses through that hole. I am considering this upgrade, but I am dreading dealing with the clutch as well. So, Greg, this comment is really helpful. Eric, thanks tons for the video. Super helpful.
I too was able to separate the booster from the adapter bracket w/o removing the wires. Big win!!
Some one mentioned removing the booster from the inside of the Jeep, I have holes in the firewall where the bolts are but they don’t exactly line up with the bolts and the nuts w the captured washers won’t fit thru the holes anyway.
Your pain and error will be the salvation for those who have yet to do this. Thanks so much for the video!
That was my goal. Hope it helps others learn from my mistake.
I just did the J8 install, I did a couple of things differently that seemed to save time and headache: 1. I installed the master cylinder to the booster before putting the booster in the jeep the entire assembly slid right in with zero problem. 2. I drilled the holes in the firewall out a bit larger so I could reinstall the 4 nuts for the booster from inside the jeep, this meant I could loosely install the backer plate and them slide the entire assembly on and bolt it all in.. I did have to relocate my twin air compressor setup, but found that moving it forward toward the front of the jeep allowed it to clear the master cylinder resovoir and still fit (barely) under the hood I was able to reuse the bracketry with a few small bends on the vice.
just hit the sub button because this was a great video
I just installed J8 Master Cylinder and Booster today also. GREAT VIDEO! Thanks for all the tips!!!!
Awesome! Happy to hear the video helped. :)
With stock brakes? How did it feel?
Dude, thanks for the tip on the PITA sensor connector. Props
Fantastic videos Eric. Master tech.
Thanks! Figured it was important to show how it went wrong to save others the from a similar fate.
A tip on fitting the M/C to the booster, trim the unthreaded ends of the two mounting bolts on the booster off and you'll be able to slide it in to place much easier. Space between the M/C and the ABS unit is really tight, the trim gets you just the amount of space you need. It is very easy to get the pedal shaft on the booster jammed on the side of the m/c piston, rather than centered inside it. Also, be very careful with the level sensor connector, easy to break those off.
Muchas gracias, realizaré este upgrade en mi Jeep Wrangler JKU 2012 automático utilizaré el booster y cilindro maestro MOPAR P5160050. Saludos desde Puebla, México.
Bienvenido, espero que te funcione.
Good job mate!
Great videos man! Nice work! How have the JK brakes been doing ? That's likely my next upgrade
The JL HD brakes with J8 MC and booster provide brake feel one would expect from a vehicle of this size. Highly recommended upgrade!
Hello. Excellent videos. I am going to do the same upgrade to my '17 JK. You mentioned that there was sensor cable attached to the stock booster, and that there was no attachment point for it on the J8 booster. How did you resolve that? Thanks!
Thanks! I carefully pulled out the sensor from the stock booster and installed it into the J8 booster. Hope that helps and good luck!
Eric Cantin Got it. Thanks!
Would it be possible to bleed the master cylinder while it is attached on the Jeep? I don't have a vise to hold it on a bench to push the plunger in. I thought I might be able to use the actual brake pedal to push the plunge and do the bleed. Also, if I bled the MC this way I could install the MC to the booster and then the reservoir after that. Am I off base here or is this feasible?
Also, I've read accounts of troubles getting the fittings tight enough to not drip when re-attaching the hard lines to the MC. Any issues w/ that or w/ getting them to line up w/ the ports?
I’ve never tried bleeding a MC while attached to the vehicle. unsure if the pedal fully pushes in the plunger through the booster.
I was able to get the lines nice and snug with a flare wrench. Definitely want to seat the line all the way in to help line up the threads. If it doesn’t easily spin onto the threads, wiggling the hard line may help align it.
Good video! From start to finish, how long do you think estimate this project will take?
Thanks! If nothing is seized, have the right tools and aren’t messing with cameras, half a day to a day.
Good video ! Do u have a BBK? How does it feel compared to stock day to day
Thanks! Yes, I installed the JL HD brakes on my JKU. Here's the video: ruclips.net/video/nyVWLHBFG18/видео.html
The day to day driving feel is so much better. The brakes feel appropriate for a vehicle of this size. I plan to do the same mod on my wife's JKU. I know I'm in a different Jeep as soon as I approach the first stop sign (pedal feel and once they engage, just a tad more pressure really slows it down). We have another J8 kit on order (actually ordered it the same day as the Crown master cylinder), its still a few weeks out.
I am about to do this mod on my JKU 12 with a manual transmission. Do you have any tips or things I should look out for?
You’ll need a separate reservoir for the clutch reservoir. Be sure you move the tub by removing all the bolts. That totally makes it easier. Good luck!
I am ready to upgrade my brakes. Do you really have to upgrade the booster? I’m in a 14 JKU. I was thinking of using the Power Stop front set up for a JL.
I had another brake issue (vacuum pump) at the time that hadn’t shown its face. Some say it works well after a good ABS pump brake bleed on the 2012+. So tough for me to say either way without trying.
I figured out the JL HD brakes would work on a JK while reading the Teraflex Delta brake installation instructions. Their kit works with the stock JL booster and master cylinder but requires the J8 upgrade for the JKs.
I highly recommend upgrading all 4 corners at once. The stock rear pads are so tiny vs the JL HD. Also the calipers are bigger, so helps maintain the fluid ratio split front to back.
Good luck and test!
Hey Eric. Picked up the brake kit now trying to find the booster. Where did you source the brake booster from? I've called several Dodge/Jeep dealers and not one can find that part number/booster.
I got the brake booster kit from the dealership. I have another on order and have been waiting a few months. The setup in this video developed an odd leak about 6 months after install…
I also had an issue with a booster pump, which might have given me a false impression that the 2012+ master cylinder was undersized.
When the new kit arrives I’ll also do an ABS pump bleed.
I have onboard air. So my bracket and twin ARB compressor goes right around the Master cylinder. So does this upgrade change the placement of any of the components? Or does it end up like stock?
All of the replacement parts are bigger, so most likely different alignments here and there. How much clearance do you have?
Could you remove the booster by taking off the 4 nuts inside the Jeep and leave the mounting plate attached? I have a lot of wiring running through that hole in the plate and I don’t want to mess with my tidy wiring.
I couldn’t find a way to remove the booster from the plate, without first unbolting the plate from the firewall.
Someone posted that they removed the master cylinder, loosen the plate and then were able to separate the booster without disconnecting their wires.
Good luck!
Appreciate the step by step, warts and all :) Did you have to run the ABS bleed procedure afterwards? I've heard conflicting opinions, looking for actual experience. TIA
Didn’t do that. Just the good old fashioned bleeding of the brakes. Cheers!
If you change the master you need to Run the abs bleeding procedure. Your brakes will not work 100% if you don't. Trust me, I used to work at chysler jeep. Lol
What are the symptoms of air in the ABS module? Mine has always acted as it should (ABS reacts the same way) and the brake lock diff works amazingly.
@@EricCantin old fashioned bleeding , lol doesn't work on modern cars with abs modules. Shoot, newer cars you need the same scanner to change the brake pads because the parking brakes are electronic now. go ask Eric the car guy or someone that's actually been in the field.
Thanks for the feedback. Will take that into consideration.
My kit comes aletas attached to the master, so my question is why I’m getting the same issue as you did before braking the master? Should I take it a part and check if they are perfect line up?
Same issue as in brake fluid ending up in the brake booster? I'd certainly check if the master cylinder is installed correctly.
Tsb on the pcv on the wranglers, the booster can act like a catch can when the pcv is failing. The fluid in your booster, is it brake fluid or motor oil?
Brake fluid. I showed how the master was bent.
What was the reason for the upgrade? Did you do a big brake kit?
I installed the JL Rubicon HD brake kit. Stock front pads are about the size of the new rear pads. Fronts are massive with a twin piston caliper.
Hope you see this one and can reply. Now that you have the JLUR brake kit as well as the J8 MC Kit have you noticed any difference in brake pedal travel before feeling brakes engage? I've had this set up for sometime now but have never felt like the pedal travel was the same as the OEM brake setup. The JL/ J8 combo definitely has more pedal travel before engaging brakes. Not a soft pedal per se, just more travel before braking seems to occur. Could it be because the JLU brake pads are forced off the rotors by the pad springs?
There’s an issue with my MC and booster, so hard to say. Been on a backorder waiting list for a while. My pedal feel is inconsistent and sometimes engages higher than other times. I never tried to cycle the ABS unit with JScan to see if that would help.
A buddy of mine recently installed the J8 MC and booster, I’ll have to ask how the brake pedal feels compared to his Gladiator.
I’ve driven JLUs and their brake pedal felt fine, so doubt that the pad springs are the culprit. My wife’s JKU with stock brake setup definitely engages sooner in the brake travel.
@@EricCantin I saw on your vid where you had install troubles with the 1st MC. I think you went to a Crown MC after that. I’ve gone thru 2 Crown MC’s. 1st developed internal leak almost immediately. 2nd started leaking from reservoir seals after 8 months. I’m now on a Crown booster and Mopar MC. I’m wondering if it could be the booster that’s the issue? I’ve pressure bled this thing probably a dozen times with no change. Ran ABS bleed multiple times also.
BTW I was just typing a long message to you on Wrangler Forum regarding this. Saw a thread where member was experiencing 1-2” pedal travel before brakes felt like they reacted. I’m having that same feeling, even w the J8 MC.
I asked my buddy. His J8 MC blew up on first use… The manufacturing quality of the components seems to have fallen off a cliff.
@@EricCantin Mopar or Crown parts? What’s he doing for brakes now?
All Mopar. He reinstalled the stock parts. He was told by the dealer at least 4 months for a warranty replacement… he might try Crown.
Hi Eric, I know I'm way late... But great video, thank you..... You mentioned running that abs procedure from your cell .... Could you elaborate.... Gonna swap to big brakes pretty quick, and MC too.... Not sure on booster yet though...... Done a grip of work on my 15 JK myself so far, I'd hate to think I needa go to the dealer to bleed the brakes.
Look into JScan OBD2. I’ll eventually do a video if back ordered parts come in.
@@EricCantin I'll check it out, thank you!
Great in depth video. I appreciate it sir. I'm looking at doing this swap is the a night and day difference?
Thanks and welcome! If you upgraded the calipers, insane difference. With stock calipers, might be too sensitive.
@@EricCantin What year is your JK? I have a 2012 and was under the impression the master cylinder may already be improved over the 07-11 JKs.
@@coreymaggio5567 It’s a 2012. The J8 has a 1-1/8” bore vs the 1-1/16” that came stock on the 2012+ (also known as the BR6).
@@EricCantin Thanks! I thought that looked like a fellow Dozer JK...I'm having trouble confirming I have the 1 1/16 bore from the factory so I'm happy you noticed a difference on your 2012.
You are getting good at replacing the master cylinder. Do you want to do mine next? Great video!
LMAO! Thanks for the feedback & offer.
at 7:00 you mentioned you didnt know where that electronic plug would go since the new booster didnt have the connection. Where did it eventually plug into?
Somewhere in the process, I realized moving the sensor from the original booster to the J8 would do the trick.
Can you please remeasure now that it is installed? I have shock tower in place and no more room. Just need to confirm measurement before I decide to order. Thanks!
Measure from where to where?
Can you please post the individual part numbers on both the master cyl., and the booster. Can’t really use the brake kit part number as a crossreference.
Have a look in the video description. Good luck
Thank you very much for your time and effort making this video and listing the part numbers.
Hello Eric, good video and comming accros i ve found about the broken MC, do you still have it? Mine got a broken ear.
MC and booster still on Jeep. Waaaaaaaaaaiting for order to arrive. My hunch is the booster is faulty.
The booster isn t as hard to find as is the Master Ciliynder ot the whole kit.I was wondering of you still have the broken master cylinder and can sale it as i got a broken ear on mine and hope i cam repair it with the parts from the one that broked on your forst install
The broken one shown in the video is long gone. Did you check if Crown still has the replacement unit? Part number should be in the video description. I think I put the part number in the video.
I was kind of reticent on Crown option as i ve read people feedback s here and there sayng it didn lasted for a whole day, others say it failed whitin a week so how s yours holding up , how it performed over the time?I?
Until I have new parts and tear it apart, tough to say if my issue is the booster or MC.
My mechanic just change the master cylinder & booster, but my pedal still going all the way to the back, any tips?? Thank you
Might have to bleed the ABS system. JScan and other tools allow to do it without the pricey dealer hardware.
@@EricCantin thanks
I just replaced my 2nd Crown J8 MC. 1st leaked internally, 2nd started to leak at the reservoir seals after 15,000-ish miles.
Question: how are you all bleeding the J8 MC to get a good pedal? Mine seems to have a lot of travel ( more than my wife’s bone stock JKU) even after a pressure bleed and ABS bleed w Jscan.
Mine felt almost perfect until the Crown MC started to leak. Must have been lucky while bleeding it. I’m still waiting for Mopar parts to arrive.
Is your brake vacuum pump working correctly?
@@EricCantin how would I know?
Have you had an issue with it leaking.. I did this about the same time you did and did the exact same thing but my rubber seal between the resovor and cylinder were leaking so I Warranty it and got a new one now 6 months later it's leaking again?
Is that an air or fluid leak?
I recently had a fluid leak, but one of the two brake lines needed just a bit more tightening. Other than that, its been reliable.
@@EricCantin one of the two rubber seals are leaking brake fluid between the master cylinder and resovor for the 2nd time in 6 months
Ohh wow. Mine is using a Crown MC, since it was available sooner. Haven’t noticed any fluid going into the reservoir.
@@EricCantin yes I had to do the same exact thing you did crown master cylinder and everything
I just checked my brake fluid level, it dropped again. Need to investigate again. The leak was definitely coming from a brake line at the MC, will have to check that it’s the only spot that’s leaking. I’ll report back over the weekend once I’ve had a chance to dig into it.
I'm sorry this happen. Once you get brake fluid in the power booster your going to need to replace it too. The seals on the inside of it will start leaking and will not hold pressure. This happen to me when I did my install so the when I installed the replacement parts I removed the ABS module out of the way and this made a room of difference. I also broke a line in the process. Not a easy job but the results are amazing.
How long did your booster last after that happened? I got all the brake fluid out, and as far as I can tell the diaphragm was still dry after the incident.
My mechanic buddy told me to go ahead and replace it so I never try reusing it. You should do a review on how long it does last.
Will report back if something happens to the booster.
Brake fluid alone will not make rubber swell. Brake fluid contaminated with power steering fluid will make rubber swell.
Thanks for "not" explaining how to release the tetaining clip underneath the dash. Great job 🤣
I didn’t know how to remove it either! 🤣
Great video man very detailed - how has the j8 booster and mc help upda help up So far thanks
It started acting up after we moved (and I chucked the old MC and booster). Seems like there was a known bad batch when I got mine. Been waiting for Mopar to have more in stock for over 18 months…
@@EricCantin how does the pedal feel with the stock booster and mc is it the same performance vs the j8 Set up
My wife’s JKU has stock braking system. My JKU has the JL Rubicon HD rotors, pads and calipers with J8 MC and booster. Even though I have an issue with my setup, it still out brakes the stock parts.
Pedal feel is off now, but was great until the issue popped up.
@@EricCantin Dam,,,, I was able to snatch one up from NORTHRIDGE 4x4 they had a few in stock I got the second to last one keep an eye on there web site for
Can that fit on JK 12 as well
Yes, the engine bay of the JK and JKU are pretty much identical. Only exception is if there’s an aftermarket part in that corner, or equipped with a manual transmission.
A manual transmission will require a separate fluid reservoir for the clutch master cylinder.
@@EricCantin Thanks but is that large Booster? can fit on JK where i can order one?
JK and JKU have the same amount of space under the hood.
I got mine from the local dealership. Some performance shops also sell it. Right now there’s a serious backlog in the supply chain. I ordered another one in March for my wife’s, and was recently told it would be back ordered until November… Hope you have better luck.
BTW, the vehicle hard lines don't line up perfectly with the M/C ports, you have to bend them slightly and CAREFULLY to line them up with the threads on the m/c.
Anyone who has done this notice the bolts on the back of the booster splay out a bit when tightened onto the adapter bracket!
To follow up on my own question: This must be a Crown Booster thing. The Mopar Booster did not display this fitment issue.
If you change the master you need to Run the abs bleeding procedure. Your brakes will not work 100% if you don't. The abs module will have air in it that only the procedure can bleed.. Trust me, I used to work at chysler jeep. Lol
What are the symptoms of air in the ABS module? Mine has always acted as it should (ABS reacts the same way) and the brake lock diff works amazingly.
@@EricCantin pretty sure you have talked yourself into thinking your brakes are 100% air free. After the procedure you will notice how much less travel your pedal will have to get it to stop.
@@EricCantin It's cool if you good with it. I just would not recommend it to people when your wrong. Please take no offense. Again , I've spent 8 years sweating my ass off for chysler jeep ram.
Thanks for the feedback. Will take that into consideration.
As a secondary voice. The abs bleed is true, while it's possible you were able to keep air out, it's not likely. This can cause an irratic braking situation in an emergency situation which could be fatal
Should change title to what not to do when changing… I truly hate/love my Jeep
What a nightmare
should have just unbolted the booster iiself from inside the jeep instead of removing the whole bracket for no reason
That would be correct for other vehicles. Impossible here without cutting holes in the firewall. No idea why they did that.
@@EricCantin not sure what year yours is but i can access the nuts for the booster from inside the jeep no problem on my 2011 jku without having to remove the mounting plate. thank goodness i can because i have a ton of aftermarket wiring running through that gromet that would be ridiculous to have to cut and pull out if i had to remove that bracket
Mine is a 2012. Different setup with the Pentastar 3.6L V6.