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XJ brake question.

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I know this is an Comanche Club, but I also own a 1990 Cherokee, 4.0, 4x4, with an automatic.

I recently did a major rework of the brakes and radiator.

For the radiator I replaced the closed system for a 92 and newer open system. A big improvement.

And for the brake's, I removed all of the ABS master cylinder, pump and brain and installed a regular hydraulic master brake booster from a 1989.


:dunno: Question?

Are the ABS calipers and regular calipers the same?

When I have bleed the brake system, the brake pedal doesn't seem that hard. :huh???:

So what can I do?

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Did you replace the combination/proportioning valve (the junction block beneath the master cylinder)?


I don't know if the ABS-equipped model used that, but I assume they must have. And if they did, I don't know if they were the same as the non-ABS proportioning valves. The XJ proportioning valve has a spring-loaded plunger inside. It appears that plunger and the O-ring sweep/seal on the inner end of it get gummed up and don't allow much (if any) braking to the rear axle. You might try disassembling and cleaning that. It's accessed by removing the bolt-looking thing in the "nose" of the proportioning valve body.


CAUTION: The spring is a strong spring. Be sure you remove the thing slowly and carefully. It'll drip brake fluid when open, so protect the painted surfaces beneath it.


Many XJers simply remove the O-ring and spring, and push the plunger all the way into the "nut." This maximizes braking to the rear wheels, but disables the proportioning function. I'll be doing that on my '88 XJ very soon ... I currently have NO rear brakes.


If that doesn't fix your problem, you probably need a new booster.

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