Brake Bleeding Problems

LibertyFlip

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Hey guys,

I bought a 2003 Liberty Sport 4x4 a little while ago with the intent to flip it - turns out I prefer it in about every way to the Blazer that I was daily driving, so I decided to keep it and fix it up a bit more. Recently the rear driver's side caliper seized up, so I ordered new calipers, rotors, pads, and brake hoses for the rear. It has 183k and a "only if I have to" maintenance history, so I figured it would be nice to freshen everything up. Last night I had everything but the hoses installed, and went to loosen the hoses on the car. Found out pretty quickly that the hoses are crimped on and that I should have been paying more attention. I hadn't twisted very much, so I twisted back to normal to see if there was any possibility of the line being intact until I order a new rear line kit tomorrow.

My problem starts here: When I went to bleed the brakes, everything seemed normal, after a few pumps I had pure fluid flowing with no air bubbles. (I'm using speed bleeder fittings). When I start the car to test the brakes, the pedal goes to the floor. When I go to bleed to brakes again I have consistently gotten a full pump of pure air, followed by pure fluid - no bubbles. I can't spot any fluid leaks, and I'm having some trouble trying to figure out where it's pulling in air. Does anyone have any suggestions? My two thoughts are that I cracked the steel line when trying to unscrew the brake hose, or that I bottomed out an old master cylinder while bleeding, and it pulls air into the system every time I go to test the brakes.

I'm happy to provide any more information, and thanks in advance for the help!
 
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DadOSix

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Does it have ABS?

Air might have traveled up to the ABS motor.

Second thought -

Are you sure the speed bleeders are sealing up with no pressure on the pedal?
 

LibertyFlip

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Does it have ABS?

Air might have traveled up to the ABS motor.

Second thought -

Are you sure the speed bleeders are sealing up with no pressure on the pedal?
It does not have ABS - and I meant to throw this in the original post, but I'm also 100% positive that the calipers are on the correct sides with bleeder screws facing up.

As to the second thought though, do you mean when the screws are tightened if they're sealing completely? If so - then no, I'm not sure of that. I was planning on swapping in the original screws today to see if that made a difference, but I hadn't considered that the speed bleeders might not be seating correctly when tightened.

It seems to me that an air leak there makes the most sense out of anything. I planned on tinkering some more this afternoon, I'll swap those in and get a helper for the bleeding and post back.
 

LibertyFlip

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Afternoon Update:

Tried bleeding with the original screws, no dice. I did notice a fluid drip from where the line connects to the caliper, and attempted to tighten the banjo bolts. I replaced the crush washers, but reused the original bolts the first go around (neither lines nor calipers came with them). When attempting to snug them down more, I of course snapped a banjo bolt.

Going to pick up a new pair with new crush washers this evening, hopefully remove the snapped bolt, and try it again. I suppose if fluid can seep out, air can surely seep in. Will update again later
 

LibertyFlip

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Evening Update:

Installed new banjo bolts and crush washers. Everything is dry as a bone, no fluid leaks, and the exact same problem:

Bleed each corner until pure fluid comes out, start car, mushy pedal, start over, first pump is pure air, past that - no bubbles.

The front calipers are always perfect from the get-go - never any air, which has me leaning towards a leak somewhere on the rear and probably not a bad master cylinder (I would think if it was pushing air, it would end up in all four corners, at least a little bit?)

I'm going to strip the plastic off of the rear hard line that I twisted and inspect for any possible cracks/leaks.
 

DadOSix

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Use Mopar brake fluid, or an equivalent quality fluid meeting SAE J1703-F and DOT 3 standards only. Use fresh, clean fluid from a sealed container at all times.
Do not pump the brake pedal at any time while bleeding. Air in the system will be compressed into small bubbles that are distributed throughout the hydraulic system. This will make additional bleeding operations necessary.
Do not allow the master cylinder to run out of fluid during bleed operations. An empty cylinder will allow additional air to be drawn into the system. Check the cylinder fluid level frequently and add fluid as needed.
Bleed only one brake component at a time in the following sequence: • Master Cylinder
• Junction Block
• Right Rear Wheel
• Left Rear Wheel • Right Front Wheel • Left Front Wheel
1. Remove reservoir filler caps and fill reservoir.
2. If calipers were overhauled, open all caliper bleed screws. Then close each bleed screw as fluid starts to drip from it. Top off master cylinder reservoir once more before proceeding.
 

DadOSix

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This is from the 05 shop manual.

It is their preferred method of bleeding.

note they recommend bleeding the junction block. I’ve never done that myself, but what if your air bubble is trapped. Air will rise in a system and oftentimes, VIGOROUS bleeding is required. When I used to wrench on medium size trucks, my lead mechanic and I would put a can and hose on each wheel and open the bleeder full. As it dripped, we would push the pedal down hard to burp air at all places quickly. Let off the pedal, and the accumulated brake fluid did not allow air back in.

after a few passes (4ish) we’d close em up and finish with a standard bleed.

Had very few problems like that.
 

LibertyFlip

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This is from the 05 shop manual.

It is their preferred method of bleeding.

note they recommend bleeding the junction block. I’ve never done that myself, but what if your air bubble is trapped. Air will rise in a system and oftentimes, VIGOROUS bleeding is required. When I used to wrench on medium size trucks, my lead mechanic and I would put a can and hose on each wheel and open the bleeder full. As it dripped, we would push the pedal down hard to burp air at all places quickly. Let off the pedal, and the accumulated brake fluid did not allow air back in.

after a few passes (4ish) we’d close em up and finish with a standard bleed.

Had very few problems like that.
Thank you, I'll give both of these a try! Am I reading the manual correctly that you're supposed to gravity bleed everything and not use the pedal to push out fluid at all? Or is that referring to pumping up the brakes with several quick pushes?

If I don't have luck with that, I'll try your shop method as well. I like the idea of pushing it hard to force out a bubble.

Will report back once I try, but it may not be until Monday. We're heading out for a weekend of camping and were hoping to take the Liberty.. but I suppose the Blazer will have to do one last time.

I really appreciate your time and help!
 

DadOSix

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Thank you, I'll give both of these a try! Am I reading the manual correctly that you're supposed to gravity bleed everything and not use the pedal to push out fluid at all? Or is that referring to pumping up the brakes with several quick pushes?

If I don't have luck with that, I'll try your shop method as well. I like the idea of pushing it hard to force out a bubble.

Will report back once I try, but it may not be until Monday. We're heading out for a weekend of camping and were hoping to take the Liberty.. but I suppose the Blazer will have to do one last time.

I really appreciate your time and help!
I read it as pumping with quick pushes as you say.
We always did it with pump 4 times, hold pedal. 2nd guy opens bleeder. Fluid runs til pedal on the floor.
Close bleeder.
Pedal up.
Pump it up.
Hold it.
Bleed, etc.- that is what my cousin trained my like when I worked as his helper fixing vw’s and volvo’s
 

jeepguy4276

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Another thing to check would be if you actual bleeder is sealing at the bleeder valve while it’s open. Meaning the parts that attach from the bleeder tool to the actual bleeder valve. All tubing and fittings must be air tight. Sometimes putting some thick grease around the bleeder attachments to help make sure they are air tight.
 

LibertyFlip

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I read it as pumping with quick pushes as you say.
We always did it with pump 4 times, hold pedal. 2nd guy opens bleeder. Fluid runs til pedal on the floor.
Close bleeder.
Pedal up.
Pump it up.
Hold it.
Bleed, etc.- that is what my cousin trained my like when I worked as his helper fixing vw’s and volvo’s
Thank you, we're back and we had plenty of fun! Everything is put back away and dried out from the overnight thunderstorms, so it's back to the Liberty.

Last night I attempted all of the above bleeding procedures, bled the junction block followed by a normal bleed, tried a few HARD pushes to force out any air bubbles, and also tried the 4 pumps before opening, no luck with any of them unfortunately.

Another thing to check would be if you actual bleeder is sealing at the bleeder valve while it’s open. Meaning the parts that attach from the bleeder tool to the actual bleeder valve. All tubing and fittings must be air tight. Sometimes putting some thick grease around the bleeder attachments to help make sure they are air tight.

Thanks for the advice! I (pretty heavily) applied lithium grease to the bleeder fittings as well as the tube last week in hopes that this may have been the problem, but that also did not make any difference.

After chatting with a few friends, spending quite a bit of time browsing others bleeding problems online, and even more time attempting to source metric inverted flare and bubble flare plugs/adapters :rolleyes: my next plan is to start plugging off hard lines as well as master cylinder ports to try and isolate the problem. At this point I'm convinced its drawing in air somewhere, but not 100% convinced it's the master cylinder.

I'm going to start with the rear hard lines at the rear distribution block, and if that fails I'll see if plugging the port directly at the master cylinder yields any different results. I managed to find all of the adapters I needed to plug things at NAPA, but may not be able to make it in until tomorrow.

On the off chance that anyone is looking for these fittings in the future, I believe the rear distribution block is M10 inverted flare, and the master cylinder is M10 and M12 bubble flare. I managed to find adapters for all of those to 3/8"-24 IFF, as well as some 3/8"-24 IFM plugs. I'm hoping they'll do the trick.

I'll report back once I've had a chance to try all of these out!
 

turblediesel

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Many years ago I replaced both of my seized rear calipers and had to bleed at the rear supply line under the hood on the ABS unit to get any pedal. If I remember right the book said to press the pedal once, bleed, repeat...
 

LibertyFlip

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Many years ago I replaced both of my seized rear calipers and had to bleed at the rear supply line under the hood on the ABS unit to get any pedal. If I remember right the book said to press the pedal once, bleed, repeat...
Thanks for the tip! I don't have ABS, and I bled the junction block a couple of nights ago without any success.

In (hopefully) good news though, I started blocking off ports and bleeding tonight - started with the individual hardlines at the rear, and then the master cylinder when those didn't work.

I blocked the rear port at the master cylinder, and still had a mushy pedal - leading me to believe the master cylinder is bad. I have not opened the front lines throughout this process other than the bleeder screws, and have never had air come out of them. Ideally I'd like to block off both ports and test, but NAPA gave me two of the wrong fitting instead of two M10 IFF adapters.. which I didn't realize until after they closed. At this point if there is air in those lines, it could only be coming from the MC unless it developed an air leak while sitting for the last 2 weeks that no fluid leaks out of. Possible I'm sure.. but highly unlikely imo. I've gone through 2 large bottles of brake fluid through my process of tinker/bleed/repeat, so I'm also confident that there's not any old water saturated fluid in those lines either.

To correct what I previously said about fittings, my Liberty has M10 Inverted Flare fittings all around, including both MC ports and the rear distribution block.

From here I'm going to order a master cylinder, replace, and report back. If anyone has any other suggestions I'd be happy to hear them! But I personally can't think of any other possible problems/solutions.
 

JeepJeepster

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I recently ran into something similar to what you are going through. After 26 years, the hose going from the frame to the rear axle went bad on my ZJ. Rear brakes were dragging. Replaced it and bled the brakes using my vacuum bleeder, didnt even move the brake pedal. Started the jeep and pushed on the brake pedal, slowly went down to the floor. What the heck??

Turns out, I had a bad master cylinder. Life is full of funny situations.

Just as a heads up, I learned a lot about the combination valve during all of this. If you press the brake pedal before bleeding the brakes it can cause the combination valve move and get stuck, thus blocking off the rear brakes. They make a tool that holds the combination valve in place while bleeding but if you use a pressure bleeder, vacuum bleeder, or just let them gravity bleed, you should be good to bleed them as you wish.
 

LibertyFlip

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I recently ran into something similar to what you are going through. After 26 years, the hose going from the frame to the rear axle went bad on my ZJ. Rear brakes were dragging. Replaced it and bled the brakes using my vacuum bleeder, didnt even move the brake pedal. Started the jeep and pushed on the brake pedal, slowly went down to the floor. What the heck??

Turns out, I had a bad master cylinder. Life is full of funny situations.

Just as a heads up, I learned a lot about the combination valve during all of this. If you press the brake pedal before bleeding the brakes it can cause the combination valve move and get stuck, thus blocking off the rear brakes. They make a tool that holds the combination valve in place while bleeding but if you use a pressure bleeder, vacuum bleeder, or just let them gravity bleed, you should be good to bleed them as you wish.
Thanks for the tip! The combination valve has been at the back of my mind through this process, but I get fluid through the brakes, and they hold enough that I can't turn the rotor by hand, which eliminates that - I would think?

The master cylinder arrived today and I got it installed - leading me to second guess a lot of things from the last two weeks. After bench bleeding, bleeding the junction block, and lots of fluid through all 4 corners I started it up and... Same pedal feel. Went to bleed and... Same "problem".

My neighbor works at an auto shop, and ended up coming over to tinker with me. Turns out I may have been having some miscommunications with the gf when we were bleeding in the past. After some testing with the neighbor, I think what I/gf was perceiving as a full air bleed on the first pump was actually the result of residual power boost. (Deduced through careful timing of communication with neighbor, and starting with a bleeder line full of fluid - no air bubbles with the soft initial pump)

I guess before I was always working the bleeder screws, and thought that the gf had made it through a decent amount of pedal travel before the fluid started flowing. Between moving to a different caliper, and taking time to get up and talk to gf as she started the car, I apparently had never started the first bleed pump with a hose already full of fluid either. Probably should have thought that through a bit more.

Tested this theory by pumping the pedal twice after shutting the car off and before starting the bleeding. When doing this, everything feels perfectly fine through the pedal during the bleeding process. Should've thought this through a bit more as well.

I feel pretty stupid for not realizing this before buying a master cylinder, but I suppose I was so caught up in the spongy pedal and the remaining sponginess after blocking off MC ports that I didn't think to consider anything else.

I used the down time while waiting for parts to start painting my rusty wheels, which I should have finished up tomorrow to go for a test drive. For all intents and purposes, I believe I'll have brakes - but this leads to yet another question:

When holding the pedal with the car off, it's solid. When I start the car it drops (booster test) and holds (MC test). Where it holds is what's been concerning me this whole time, the pedal drops about 2.5 inches before it becomes solid and holds. I'm unable to pump up the pedal any further than that, it always holds in the same place.

Is it possible that this is a booster problem, or is this normal travel for KJs? It seems way further than any of my other vehicles, but I didn't own/drive this one very long before starting this project and I don't remember what the brake feel was like prior to the new rear brakes.
 
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