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Master cylinder and booster swaps advice

Vince

NAXJA Forum User
Location
England
Are Jeep master cylinders plug-and-play between booster and master cylinder as long as you don't mix single diaphragm boosters with master cylinders for dual diaphragm boosters and vice-versa? This will be the first booster/master cylinder I have changed on a Jeep.

My RHD export model 1993 XJ has developed a fault with no brake pressure on the rear circuit. It was originally equipped with 4-wheel ABS on disc and drum brakes but has been running for twenty years with ZJ rear discs with the ABS disabled.

My Jeep failed annual inspection recently on lack of brake force on the rear axle. I assumed the calipers had seized so I replaced the rear calipers and pads yesterday. However, before doing so, I noticed that I could not bleed any brake fluid from the old ones. I have a firm brake pedal and my booster is working fine on my front brake circuit, but I can't bleed the rear circuit.

I have no fluid leaks. The ABS pump is still present and still has the OEM return lines to the reservoir. I assume I have a problem either with my master cylinder or the proportioning valve.

My current booster is a Mopar 52007236, this is matched to an iron master cylinder with a dual filler cap reservoir. There are two fluid return hoses entering the base of the reservoir from the ABS pump. It looks like it is a dual diaphragm booster. It has some electrical gizmo fitted to the booster casing that's around 4" long. No idea what that is?

Economical replacement parts are challenging to find here locally in the UK but RockAuto and FedEx usually get them in my hands within 5 days. I would like to take this opportunity to completely remove the remnants of the old ABS system when I replace the master cylinder. I will remake all of the hard lines so that it has a new non-ABS brake system.

From what I can see, a new booster equivalent to a Mopar 4762163 looks like the part I need. They were originally fitted to 1994 Jeep Grand Cherokee ZJ. This is a dual diaphragm booster that looks identical to what I have now.

My brake pedal only has the single brake light switch (black housing). I haven't pulled the booster yet, but the rod looks like it is the round style (no flats).

To this '94 ZJ booster, I would like to install a 1996 XJ non-ABS master cylinder (single cap reservoir) for a dual diaphragm booster equivalent to Mopar 04761941, 04882872, 4761941, 4882872.

I can't risk going for an assembly that is longer than my current setup as my engine coolant bottle is immediately in front of the master cylinder.

I am thinking of replacing the factory proportioning valve with a Wilwood valve if it is broken.


Plan A:
Remove proportioning valve. Strip it down to inspect. Rebuild, refit and test by bleeding the system.


Plan B:
Do Plan A first.

Remove master cylinder. Rod will determine if the booster is single or dual diaphragm.
Order new parts as above.
Make new hard lines.
Fit new non-ABS system, bleed the system and test.
 
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