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WJ Master cylinder and booster swap problem

Talyn

NAXJA Forum User
Need some help here on my 2000 XJ

First off I have the twin pot Ausi(GoJeep) caliper/rotors in the front and ZJ rotors/calipers in the rear. ZJ Prop valve. They work great. I was using the stock MC/Booster and while the braking was great I wanted to change the pedal feel. It was a bit firm and wanted more of a stock feel. Taking Fordguy's advice I swapped in a WJ MC and booster.

Swap went fine and everything fits. I first bench bled the WJ MC and then pressure bled it after install along with the prop/combo valve (ZJ).

When I press the pedal the initial feel and engagement is great. However, after anything past mid foot pressure and into heavy braking it feels like the system is not putting out any more pressure and the pedal bottoms out. No leaks in the system. Pedal drops a little when the engine is started, so I don't think the booster is bad. It feels fine with consistent braking until you really push the pedal, then it feels like it hits a stop and it won't apply any more pressure.

I re-bled the system last nigh using someone pumping the pedal while I open the bleeder valved. RR, LR, RF, then LF. No difference. Thinking of going back to the stock mc/booster, but the WJ setup should work.
 
The WJ master/booster has the same specs as your stock one, there is no upgrade..

I've seen several (and installed a couple myself) WJ master's where the front/rear lines got reversed, you get similar results to what you are reporting.
 
According to specs the master is the same diameter, but there is a difference in the booster.

I don't think I reversed the lines, but I will check that. The stock lines bolt up in the same location.
 
According to specs the master is the same diameter, but there is a difference in the booster.

I don't think I reversed the lines, but I will check that. The stock lines bolt up in the same location.

I seem to recall them being reversed from stock and that being the issue, but its been a while...
 
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