Mopar J8 Booster & Master Cylinder Alternatives?

[WarthogJK]

2 minutes ago, Crawl2Camp said:

 So even the J8 was spongy and the pedal would drop a bit before engaging the brakes?  Grrrrreat.

 

Not initially.  When it the Crown J8 failed x 3 ...it went to the floor every time.  The replacement OE 1 1/16 bore is not spongy in my opinion.  Not like stock on stock wheels and axles but definitely not spongy.

[WarthogJK]

12 minutes ago, Crawl2Camp said:

If im not mistaken, the 1 1/16” master is used in all 2013+ Jeeps from the factory.  I’m currently using my stock unit (S/B this as I have a MY14) and the pedal is spongy. I’ve bled it three times, then had it flushed and bled at a shop per requirements including ABS.  I’m a bit worried to see how it will work out on the trail, because with my stock axles the brakes would get worse in 4 low and low RPM.  

 

I also replaced the soft lines at the calipers with braided lines which improved the brake pedal.

[Crawl2Camp]

3 minutes ago, WarthogJK said:

 

Not initially.  When it the Crown J8 failed x 3 ...it went to the floor every time.  The replacement OE 1 1/16 bore is not spongy in my opinion.  Not like stock on stock wheels and axles but definitely not spongy.

Maybe I just need to try a new OEM master then and see if I get an improvement.  

[Crawl2Camp]

1 minute ago, WarthogJK said:

 

I also replaced the soft lines at the calipers with braided lines which improved the brake pedal.

 yeah I have all aftermarket lines.  Just swapped them all for longer (28”) lengths. 

[WarthogJK]

34 minutes ago, Crawl2Camp said:

Maybe I just need to try a new OEM master then and see if I get an improvement.  

make sure you get the larger bore. 

[Nice Little Jeep]

 “I went to my local auto parts store and they had the 1 inch (small) and the 1 1/16 inch bore (medium).  They have different part numbers.”

 

what’s the part #

[Crawl2Camp]

Just an FYI they are currently manufacturing the J8 booster and master cylinder again.  I got a ship date direct from Mopar via Morris 4x4 who I bought it from over a year ago, that it will ship from Mopar by the end of this month. (Given a date of 10/24/22)  I talked to Northridge today and they also conformed this is correct and that it is back in production. 

[Crawl2Camp]

1 hour ago, Nice Little Jeep said:

 “I went to my local auto parts store and they had the 1 inch (small) and the 1 1/16 inch bore (medium).  They have different part numbers.”

 

what’s the part #

I think the 1 1/16” bore master is:
68091278AE

Just ensure it’s a master cylinder specifically for a MY14-MY17 and you should be good. (The MY12 and older were the 1” bore)
 

[Nice Little Jeep]

This was a good read last night at midnight while I couldn’t sleep this topic put me to sleep. I found that Mopar/Jeep dealerships only can sell the complete J8 system. Now I have found individual brake master parts are sold by Mopar but none of them are in stock. The only product that’s in stock is Crown parts. so that’s what I assembled mine with everything is crown except the brake master reservoir which is Mopar. I’m on my second master cylinder from Crown with a zip tie securing the reservoir to the master cylinder because I think that’s the real problem I’m having. Time will tell.

 

 Note: my brakes have never not worked during this process. I’ve had 100% phenomenal brake pedal just got brake fluid seeping from between the reservoir and the master cylinder.
 

I have used DOT3 in this build from the beginning and my brakes have worked. phenomenally well from the beginning.

 

sorry if I’m late to the party.

[fiend]

On 10/17/2022 at 11:27 PM, Crawl2Camp said:

Just an FYI they are currently manufacturing the J8 booster and master cylinder again.  I got a ship date direct from Mopar via Morris 4x4 who I bought it from over a year ago, that it will ship from Mopar by the end of this month. (Given a date of 10/24/22)  I talked to Northridge today and they also conformed this is correct and that it is back in production. 

Good news. I think I got the last one on Northridge’s shelf last fall. It’s been working well, even though I never did do an ABS bleed. 

[Nice Little Jeep]

On 10/17/2022 at 11:27 PM, Crawl2Camp said:

Just an FYI they are currently manufacturing the J8 booster and master cylinder again.  I got a ship date direct from Mopar via Morris 4x4 who I bought it from over a year ago, that it will ship from Mopar by the end of this month. (Given a date of 10/24/22)  I talked to Northridge today and they also conformed this is correct and that it is back in production. 

That is good news, if my current set up doesn’t work then I’ll put an order in for the complete unit from Mopar.

[AJK]

It's in stock now.