Bleeding brakes - what am I forgetting?

[JefCooks]

Hey everyone.

 

‘92 w/ 8.8 (disc), ZJ BB/MC and rear prop valve delete. My rear driver side shock nut worked itself off during an off-roading excursion and then my shock worked itself off the post, jammed up into the wheel well pinching my rear brake line and eventually wore a hole in it. I pulled the old brake lines and ran a new hardline but now my rear brakes won’t bleed. Ive used a one-person bleeder and hand pump vacuum bleeder no go. I plugged and bypassed the distribution block under the hood going straight from the MC to the rear brakes and still nothing. What am I missing or doing wrong? I’ve done lots of brakes and had to totally redo the system when I swapped the 8.8 so I know I got it right before. 

[Pete M]

did your master get bled dry?  you may need to bench bleed it first.

[pizzaman09]

I'm generally a fan of gravity bleeding, fill the reservoir and then crack the bleeder.  Walk away for 10 minutes and see if you have fluid coming out the bleeder.

[Limeyjeeper]

Are you doing passenger rear first then driver rear the passenger front then driver front? It is critical you bleed in that order, or you will never get the air out because of the way the proportioning valve works.

[JefCooks]

Pete, Master Cylinder has been bench bled twice (while installed though if that matters). No air left in it. 

Limey, Starting at passenger rear brake every time. No difference. 

Pizza, I did a gravity bleed. It took a long time because I ran a lot of fluid through each brake to make sure the entire line was flushed but as soon as I closed everything up my pedal was still super soft. 

[JefCooks]

One of the key issues I’m having is that I’ll star bleeding rear passenger brake and it will move some fluid through, I’ll top off reservoir and then no more fluid will go into the system. I can pump the pedal 50 times with no change in fluid level in the MC. What would be causing this to happen? I thought it was the fail safe in the distribution block which is why I bypassed it but even with a direct connection from MC to rear brake line, the same thing is happening. 

[Pete M]

what if you unhook the line from the rear?  maybe there is something clogging the wheel cylinder?

[JefCooks]

I’ve replaced the BB and MC as well as rebuilt both rear calipers and blew out the lines while I had everything apart, there shouldn’t be anything in there anymore but if I’m not missing any major steps to bleeding then it must be something mechanical like that. 

[mjeff87]

Did you reset the valve in the prop block (the thing that the 2-wire connector attaches to on the top)?  It's designed to trip if there's a failure in the system and direct all pressure to the front brakes.  Is your BRAKE light on in the dash panel?  If yes, you probably need to reset the prop valve.  Try putting the MC lid back on, then pressing HARD on the brake pedal while sitting behind the wheel, with all the bleeder screws closed.  If you hear a little click (and the light goes out), it has reset.

 

 

[Eagle]

Which outlet on the front distribution block did you plug?

 

 

[JefCooks]

MJeff, the shuttle valve did trip a couple times and each time I reset it. The main reason I bypassed the dist block was to avoid any issues with the shuttle valve. 
 

Eagle, originally I plugged the bottom front. It worked great like that for years. Now I have all the front holes plugged and line from MC goes directly to rear break hard line. 

[OldSch88L]

Do you still have the rear load-sensing valve?

[JefCooks]

No, rear valve is long gone

[Pete M]

is the pedal spongy with the engine off or on or both?

[JefCooks]

Pedal is soft anytime I hook up rear brake line. When I have the rear lines plugged and it’s just the front, pedal feels nice and firm. 

[The86manche]

How is fluid flowing from both ports in the master? If you disconnect it from the distribution block and run the lines into a bottle or something and press the brake foes fluid flow nicely?

How are your soft lines? 

[JefCooks]

I haven’t inspected the flow from the MC, just routes the lines back into the reservoir to bench bleed. I’ll grab a clear bottle and inspect. 

[PIKE]

I replaced rear brake calipers on my 97 Grand Cherokee, there is a right and a left. I put them opposite of where they should be. No brakes.

[PIKE]

On 6/3/2023 at 1:17 PM, PIKE said:

I replaced rear brake calipers on my 97 Grand Cherokee, there is a right and a left. I put them opposite of where they should be. No brakes.

 

 

Am I the only guy that has ever done this?   Or the only one to admit doing it.    

[87MJTIM]

1 hour ago, PIKE said:

 

 

Am I the only guy that has ever done this?   Or the only one to admit doing it.    

 

Nickintime has a YouTube video where he coverts to rear disk brakes.  During the video, he mounted the calipers on the wrong sides - the bleeders were on the bottom of the caliper.  I was shouting at the video (yes, I was shouting) that they were on the wrong side.  Later in the video, he shows the calipers on the correct sides - bleeders up top.  Funny, he didn't mention finding and fixing the error.

[PIKE]

1 hour ago, 87MJTIM said:

 

Nickintime has a YouTube video where he coverts to rear disk brakes.  During the video, he mounted the calipers on the wrong sides - the bleeders were on the bottom of the caliper.  I was shouting at the video (yes, I was shouting) that they were on the wrong side.  Later in the video, he shows the calipers on the correct sides - bleeders up top.  Funny, he didn't mention finding and fixing the error.

 

 

Thank you, I don't feel so bad now. That's exactly what I did.  Wish you were there to yell at me at the time. Lots of peddle pumping and bleeding until I figured it out.

 

I'm wondering if that's what JefCooks did too.  Hope he responds. 

 

I'm guessing a new thread could be started about repair faux pas. My rear brake debacle is not the only one I have made.  

[JefCooks]

Reviving an old thread. I broke down and took the truck to a local Jeep garage and they don't have a definitive answer for me either. I'm going to bring the truck home and keep working on it because evidently the experts aren't much more help. I'll keep everyone posted.

 

Pike: The rear disc brakes are original to the 8.8 that I swapped in. While rebuilding the calipers I did them one at a time so as not to mount them incorrectly.

[JefCooks]

Wanted to close this out to help anyone else.

TL;DR: It was the soft line going to passenger rear brake and caliper were upside down.

 

The whole story: The truck was pushing fluid just fine at the distribution block so I hooked up the hard line and disconnected the other end where it T's to the left and right rear brakes, still good flow. I continued doing that all the way to the soft line between passenger rear caliper and the hard line that runs along the rear axle. The soft line would only drip a little fluid so it was clogged. I had blown the hose out with compressed air and brake cleaner a couple times and seemed clear but when trying to push brake fluid through the system it was a no-go. So I swapped it out and started bleeding the system. Still no-go, exact same issue. Then I was looking at the brakes and noticed the calipers were upside down. I honestly don't remember taking them off at the same time but I'm an idiot so this actually makes sense. Swapped the calipers to the proper side and bled the brakes like normal.

[cruiser54]

Thanks for the update.