Gonna try a JY master cylinder. Difference between ZJ m/cs? - JeepForum.com
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Unread 03-06-2013, 06:15 PM   #1
Maine1994ZJ
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1993 ZJ 
 
Join Date: Feb 2013
Location: Phippsburg, Maine
Posts: 678
Gonna try a JY master cylinder. Difference between ZJ m/cs?

While poking around the local JY I've noticed that some ZJs have a m/c with an oval-ish reservoir with only one cap, while others have a rectangular reservoir with 2 caps.
None of them had a rear axle left in them to verify my theory, but I came to the conclusion that the 1 cap setup is for 4 wheel discs, while the 2 cap setup is for rear drums. Mine has drums and the 2 cap setup.
Is my logic correct?

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Unread 03-07-2013, 05:45 AM   #2
Marcos
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Actually, it had to do with the ABS system. The 2-cap was used on the early (93-94) Teves MkIV system. The single cap was used on '95 up with the MkIVg (95-96) or Mk20(97-98). The early ABS had 2 tubes going from the ABS unit to the reservoir that drew fluid during an ABS stop to restore the pressure that was bled off and keep the brake pedal level. These models have a pedal travel sensor attached to the brake booster. The MKIVg replaced all this with built-in hydraulic accumulators. There may have been differences in the master cylinder itself between disc and drum vehicles in '94.

'93 were all rear drum, '94 had rear disc on Limited only, '95 and up all had rear disc.
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Unread 03-07-2013, 06:59 AM   #3
Maine1994ZJ
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1993 ZJ 
 
Join Date: Feb 2013
Location: Phippsburg, Maine
Posts: 678
Thanks for the info. I've got a brake issue that's driving me nuts and I've narrowed it down to the m/c, since I've bypassed the ABS pump with steel lines. Just trying to reaffirm that I'm not crazy...
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