eggdashure

Hey guys,

I'll try and make this quick. Built an 8.8 4.10 axle, swapped it on the Jeep in place of the 8.25. 8.8 just isn't working out, much to my chagrin, so I decided to swap the 8.25 (that had a working disc brake conversion when pulled) back in.

As I'm hooking everything back up with the 8.25, I notice one of the brake lines was nicked during installation. So, I trotted down to O'Reillys, and picked up a new line off the shelf. When I returned home, I found my plug had dislodged and brake fluid spewed all over the garage floor.

Master was dry.

So, I bled the master (no bubbles) then started to bleed the passenger rear, but I can not get it to stop pulling bubbles (using a vacuum bleeder) after 2 large things of fluid. Lines are as tight as I can get them. When I push on the pedal, it falls all the way to the floor. It will tighten up after a few pumps, but if I stop pumping for 3 seconds its back to the floor.

If I pump it several times and hold...it does not fall to floor, so I think the master is ok.

I'm out of ideas and turning to the masters for help.

Any help is appreciated!

Petervaz1

I did the same swap with the same problem. Ended up I had the calipers on the wrong side. Make sure bleeder valve is on top.

98XJ40K

Also make sure you put the brass washers on both sides of the banjo bolts. Had the same issue once, just turned out to be a case of the DA for me.

eggdashure

Yea, I made this mistake when I initially set up the conversion. They are on top and I had the system functioning when I yanked it.

I have copper on both sides of both bolts. I've cranked these suckers down tight too.

Thanks guys, good things to check!

Mullet Bullet

Fill the res. crack a front bleeder and wait until it leaks fluid. Do this to each wheel then try using your power bleeder.

Petervaz1

My vacuum bleeder draws in air from the valve so I zip tie it to the valve. Did U bleed all 4 calipers?

eggdashure

Yea, the first time I went through all 4 lines (PR, DR, PF, DF) and had a helper pushing the pedal while I bled the lines old school...but the pedal still fell to the floor. I'm really starting to think the steel lines I got from O'Reillys are not sealing properly. That's the only change I've made to the system.

Unfortunately, the Stealership takes a week to get OEM lines in.

Do they make a Teflon tape of sorts for brakes? I would figure the fluid would just eat through most things...

Petervaz1

I don't think so? I wouldn't want a bandaid on my brakes anyways. I once had a steel braided brake line leaking internally maybe u should check them out pretty well. Also bench bleed?

hbracing13

I had the same problem when I did the wj booster and master. After bleeding the system the pedal would go to the floor. Did it again same thing even. Did it the old way and make it better but not much more, did it again with the vac and while pumping the pedal that worked. And has no air bubbles after the first vac.

eggdashure

Well...still working on this. Thank goodness my parents have an extra vehicle I can use. They like the exposure it is getting for possible sale.

I ended up replacing the Master Cylinder, 1) Because I was out of ideas and 2) because I was seeing little black floaties all over in the reservoir, like rubber from a seal. Figured I might as well while I was at it. Of course...that did nothing to improve my situation. Oh, and I bench bled that sucker for an hour! No bubbles anywhere.

Tonight's idea is to grease up the bleeders on the rear to prevent bubbles from seeping through the course threads. Up front, I get a vacuum connection from just a quarter turn of the bleeder. In the back, I start with a little vacuum and immediately begin pulling bubbles right after cracking the bleeder. So air is getting in somewhere...from what I've read, the bleeders are the most likely suspect.

Here's hoping.

If not I may tailgate someone to work tomorrow!

Bustedback

Don't grease up the bleeders, you could possibly contaminate the system and cause some damage to the rubber in the hydraulic system. Do not use Teflon tape, it's not for flare type fittings anyway. Teflon tape is not really a sealing agent, it's more of a lubricant for the tapered pipe threads as you tighten them. At least that is what my hydraulics instructor told me. Try bleeding the brakes the old fashioned way, I've never had good luck with a vacuum bleeder. Pressure bleeders work better.

dohc91gli

Probably beating a dead horse here, but have you tried breaking all the bleeders open and letting it gravity bleed for a good half hour or so? I wonder if there is some air in the proportioning valve?

eggdashure

I think it's time to try the gravity bleed. I have enough hose now for all 4 lines from all the gadgets I've tried.

Thanks

eggdashure

Things are getting worse now...

It used to take 3 pumps to get pressure on the pedal. Now it takes about 7 or 8 quick pumps of the pedal to get it off the floor (engine off) to where there is some pressure vs. just going to the floor. I gravity bled the system and saw no bubbles at all when I closed up the bleeders.

What has been done so far:

- Re-Installed 8.25, removed with known good brakes
- Replaced both rear hard lines
- Replaced (and bench bled for an hour until ZERO bubbles) a new Master Cylinder
- Traditional Bleed
- Vacuum Bleed
- Gravity Bleed
- Head bleed-ing from banging it on the wall!

I replaced a drum wheel cylinder when the 8.25 still had drums. I installed the rear disc conversion on the 8.25, bled and had no issues. I put the 8.8 on, bled the lines and had no issues, what gives this time?!

One thing I will note (again, engine off)...best way I can describe it...is a slight squishing sound when there is pressure behind the pedal. I only hear it if I keep pumping and the pedal has pressure behind it. Hope that makes sense.

JerrytheJeep

What happens when the engine is running? I think it's your booster.