Brake help!!!

[Daronw]

I’ve got an 86 MJ and I’m having a really tough time with the brakes. I’ve replaced both rear wheel cylinders, both front calipers, master cylinder, all three rubber lines, rear steel lines on the axle and the left front steel line. I’ve looked at all the other lines and none appear to be leaking. The wheel cylinders, calipers and master cylinder show no signs of leaking. I’ve bled and bled. I get a firm pedal but as soon as I start the truck the pedal goes to the floor. 
 

I disconnected the booster vacuum hose and the pedal stays stiff but there is very little braking action. I put a vacuum pump on the booster and pumped it up to about 10 pounds of vacuum. The pressure held for over an hour until I released it. The booster and check valve don’t appear to be the issue. 
 

What am I missing here? Could it be the proportioning valve below the master cylinder or the load sensing valve by the rear axle? I’m scratching my head as I’m running out of things to try. 

[fiatslug87]

There'a an MJ specific bleeding procedure it's in the DYI section, try that if you haven't.

 

ps. welcome, post your VIN in the registry and start a build thread.

[Daronw]

Thanks I’ll look for it.

 

[Chad R]

Did you have this problem before you started or is this after you changed everything  

[ghetdjc320]

If you haven’t tried this already, use some speed bleeders and pump at least a few oz of fluid through each wheel cylinder/caliper. The oem bleeding process is a pain but it’s the only effective way to get the stock system bled.

[Daronw]

The truck had been sitting for many years but when it was put away the brakes were fine. I decided to change all the parts because of it sitting. Ran out of time today to try that bleed procedure. Hope to get it tomorrow. 

[Chad R]

Check to make sure you did not install calipers on wrong side, make sure blenders are at the highest point on caliper. Did you bench bleed the master cylinder if you didn’t you will never get the air out of system. If you don’t double check calipers and not bench bleed you could run gallons of brake fluid and never get the air out

[Daronw]

Calipers are on the correct side and I did bench bleed the master cylinder. I’m pretty sure it’s the line to the load leveling valve. Thanks for the help!