i had the same problem. i also upgraded mine. but for me it happened maybe once a month. fluid levels were fine, vaccum was great. for me the issue was the rear drum brakes needed to be adjusted they dont like to auto adjust anymore. try tighting up the rear brakes and see if that fixes it

 

been ther done that keep ideas coming ive tried all the tricks automotive field allmost all my life its gonna be something different.

 

maybe its just a jeep thing...

 

Man, there's only so many components to this thing...

I think you've just lost your mind.

Hallucinations.

 

Are the master cylinder part numbers the same between the dual and single boosters?

 

Mine's a different master... but I used a 04 WJ booster/master assy.

 

Just curious, if maybe he's still using the single diaphragm master with the dual booster. It "may" be overpowering the master.

 

Overpowering the master will cause pressure loss. Seen it in a few E series Ford vans. The pressure blows right past the rear seal in the master and causes the fluid to either fill the booster or be sucked into the engine via the vacuum line.

 

That's what I was implying. I'm just wondering if it is enough to overpower it

 

Upgraded mine from junkyard 96XJ master/booster assy.No problems so far.Huge improvement in brake perfomance.
Thinking m/c leak by as well.

 

Exactly

No

impossible completely different animals

three different masters same thing.

Bone dry every time pulled

 

All was fine for about two years now gonna try another booster if that dont fix it gonna get big rock and chain throw out window when stopping ...lol...

 

Try a late model WJ booster. At the least they look nicer.

 

I have upgraded to double booster allready...over 2 years ago ...

 

I know. I was just suggesting a different one when you swap it out.