Thread: 1994 ZJ ABS brake bleeding issues

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  1. #1 1994 ZJ ABS brake bleeding issues 
    Junior Member dragordie's Avatar
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    Replaced rotors calipers brake lines fresh fluid. I have Bleed my brakes 5 times now 3 with my Vac and twice old conventional way 2 people. Still The driver side rear and driver side front will not bleed. Any ideas?? What is this about DBR tool. I don't have OBD data link connecter. That is its not on the pass side at or around the overflow tank.
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  2. #2 Re: 1994 ZJ ABS brake bleeding issues 
    Senior Member Ken L's Avatar
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    "Will not bleed" meaning the air won't stop coming out or you're not able to crack open the bleeders? I've never needed a special tool to bleed the brakes on my '96, but after replacing lines I've had to bleed them a crap load of times to get all the air out. If I remember right, I had to leave it sit overnight to get all the air to settle to a couple of spots and then bleed it. Then I pumped the brakes like crazy until they were rock hard and cracked the bleeders, doing it the two-person method.

    Not meaning to be a Dick, but you're bleeding it passenger rear-driver rear-passenger front-driver front, right? There really shouldn't be a connection between the driver's front and driver's rear, two separate circuits.

    I'd also try unplugging the electrics to the ABS pump and starting again.
    Ken L
    '96 ZJ with stuff
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  3. #3 Re: 1994 ZJ ABS brake bleeding issues 
    Senior Member Ken L's Avatar
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    Oh, one other thing I just thought of. If you replaced the fluid, did you bench bleed the master? Still shouldn't be a connection between the driver's front and rear, but if all the fluid came out the master needs to be bled first, before the rest of the circuit can be filled.
    Ken L
    '96 ZJ with stuff
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  4. #4 Re: 1994 ZJ ABS brake bleeding issues 
    Junior Member dragordie's Avatar
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    bench bled M/C broke open all bleeders gravity bleed. capped every bleeder off. started with the rear pass and drivers rear to front pass than driver. I get fluid from front and rear pass bleeders nothing but air from driver front and rear. even when power bleeding. Anyone just removed their ABS. I have 4 wheel disc brakes it is my DD / rock rig.
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  5. #5 Re: 1994 ZJ ABS brake bleeding issues 
    Senior Member Ken L's Avatar
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    I haven't removed the ABS, all I did was unplug everything and took out the relay in the underhood power center. I haven't needed the room under the hood yet, but it's and option to remove the ABS mechanics in the future if I need to.

    Don't know what else to tell you. As I'm sure you're thinking, this shouldn't be that difficult.
    Ken L
    '96 ZJ with stuff
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  6. #6 Re: 1994 ZJ ABS brake bleeding issues 
    Senior Member Grand Slam West Planner K2's Avatar
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    I pulled my abs stuff. You will need to bend new brake lines to attach to the old lines.
    02 WJ, Lift, dents, noise and smoke.
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  7. #7 Re: 1994 ZJ ABS brake bleeding issues 
    Junior Member dragordie's Avatar
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    So if I remove all the ABS components I will also need to replace the M/C do to the fact I has 2 large like fuel lines from the M/C to the ABS pump. maybe 96 or newer M/C? and than add a T to the front lines to single to the M/C? and should be able to keep the original proportioning Valve do to have 4 wheel disc brakes
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  8. #8 Re: 1994 ZJ ABS brake bleeding issues 
    Senior Member Grand Slam West Planner K2's Avatar
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    On my 95 I think I got adapters for the master cylinder and used same size lines.
    02 WJ, Lift, dents, noise and smoke.
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  9. #9 Re: 1994 ZJ ABS brake bleeding issues 
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    I ran into something very similar on my WJ, I imagine it’ll apply to a ZJ.

    First though- nothing but air from driver front and rear? If I understand what you meancorrectly then air must be getting in somewhere?

    In my case, my WJ sat for >1 year until I got around to swapping the motor. Once it was running again, the brakes were really really spongy. No matter how much I bled them it didn’t help, finally had a shop do it and they had no better luck. Replacing MC , booster, and calipers didn’t help. I finally removed the ABS module entirely (it’s been disconnected for 14 years anyway. It still was a pain to bleed fully, but it finally came around. I also swapped in a MC from a ‘79 grand marquis to better handle the larger callers I have (D60 and 14b), but assuming you have stock calipers you shouldn’t have to worry about anything like that.

    My best guess what was happening? If you get air in your abs module, you have to cycle it using a scanner like a shop will have- your home scanner can’t do it. If it’s not cycled, air can get trapped in the little pistons that normal bleeding won’t remove. I suspect that, after sitting so long, one of the pistons in the ABS module was seized with air trapped in it, so even though the shop did cycle it, it still has air in it. Side note- if one was stuck, wouldn’t shop computer pick that up? Dunno, but this was the best explanation I could come up with.

    As far as bypassing the ABS module- 2 lines out from MC to ABS, the rear line is for the front brakes, front line is for rear brakes- really important not to mix that up! The ABS module has 5 lines- 2 in, 1 out to each front wheel, and 1 out for the rear. Just disconnect all the lines, use a tee to connect your 2 front lines, then run a new line from the rear port on the MC to the tee. Cut the fitting off the rear line and replace with whatever size the front port on the MC is.

    I had to leave the ABS module connected or my speedo didn’t work. You could probably trace and splice the wiring to bypass it if you really want to take the thing out but it wasn’t worth the trouble to me.

    I got this flaring tool on Amazon- way easier to use than the common type for flaring lines in place on the vehicle (it’s really easy to use, just practice a couple of times first).
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


    Keep in mind that all the other drivers on the road count on you to have working brakes- if you’re not 100% confident in your ability to do this, don’t take a chance on it.


    On a separate note- hey guys, been a while!
    Last edited by FearTheDentist; 04-23-2018 at 04:28 PM.
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  10. #10 Re: 1994 ZJ ABS brake bleeding issues 
    Junior Member dragordie's Avatar
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    FearTheDentist: Good information.
    I cannot hook my OBD 1 or 2 scanners to my ZJ being it’s a 1994 Neanderthal . I feel extremely confident that I can accomplish ABS deleteon my grand. With no fear to the Public. I was told to drive up and down a gravel road and hit mybrakes to activate and cycle the ABS pump. Think it’s a wise tail is why I’m asking if anyone has raninto this issue before on a OBD1 ZJ.
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