Bleeding ABS after Master Cylinder change -
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post #1 of 4 Old 06-23-2021, 11:50 AM Thread Starter
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1993 ZJ 
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Bleeding ABS after Master Cylinder change

So I started to change the Master Cylinder last week. RockAuto sent the wrong part so the 93' ZJ 4.0 sat with the lines from the Master Cylinder and proportioning valve disconnected for about a week (hindsight says this was a bad move). After the new Master cylinder was bench bled and installed, I realize a bit of air probably got into the ABS. I wasn't initially concerned with air getting in the lines and such because I was going to do a flush, but I'm unfamiliar with the ABS.

I haven't bled or drove it yet, gonna do a standard bleed and see where that gets me. Any ideas what I can do with this ABS?

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post #2 of 4 Old 06-23-2021, 01:13 PM
Mr. Puddles
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1996 ZJ 
Join Date: Mar 2018
Location: Little Elm
Posts: 934
Dealer for sure. Or you can call your local service facility (Firestone, Goodyear, NTB, ect.) and ask them to verify if their scan tool will actuate the ABS unit.

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2002 Dakota aka Winnie aka Mad Max
1996 Grand Cherokee aka Puddles aka Pikey Life
Originally Posted by kg6mov View Post
The 4.0 is dumb old tractor motor, itís too stupid to know itís supposed to die.
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post #3 of 4 Old 06-24-2021, 06:02 AM
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Most shops most likely wont be able to hook up to a 93. Before I had a MT2500 to bleed the brakes, I would raise up my Jeep and with it running in gear, apply the brakes. The ABS would go crazy. Had my vacuum bleeder hooked up while doing this.

1994 ZJ-I6 w/270,000 mi
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post #4 of 4 Old 06-24-2021, 09:21 AM
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Location: Florida
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Welcome to the forum.

This reply shows usage of my DRB II tool to bleed the ABS module.

My suspicion is that a normal bleed is required when servicing the brake hydraulic components, not also requiring the ABS bleed using the DRB II tool, unless somehow the ABS was activated to contaminate internal fluid during the service. I am unaware of how that contamination / activation could happen.

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