Brake issues on a 89 XJ

I recently replaced the master cylinder on my XJ due to a complete failure, pedal went to the floor. Jeep had sat for 10 years prior. The brakes were bled and brown brake fluid was forced out, new brake fluid installed. Taking the jeep out for a road test I had a very firm brake pedal with not much stopping power. We bled the brakes again to confirm we had all the air out, still had a firm pedal but not much stopping power.

After doing some research i determined that my power booster was in need of replacement also, which i did. After bleeding the brakes, yet again, my pedal isn't what it should be i feel.

My pedal seems to have no effect on the brakes for the first half of pedal stroke and then the brakes come on hard. I need to modulate them carefully in order to avoid locking them up. I've adjusted the pushrod that enters into the master cylinder multiple times and have it adjusted to where my brakes aren't dragging, heating them up.

I'm at my wit's end trying to figure out what to do next. I know my power booster is working properly as when the engine starts you can feel the additional assistance. I'm either going to put a new master cylinder on it or buy a master cylinder/power booster combo to alleviate my issues.

One thing i haven't replaced is the proportioning valve. Would this be a consideration eing that there was dirty/contaminated fluid passing through it? I've also checked the rear wheel cylinders, hard and soft brake lines, front calipers for leaks and there are none

Any suggestions would be appreciated

I have an 89, did a new master and booster to get a better brake pedal, I just got a harder pedal but not any more stopping power. Renix guys agree that it’s because of the single diaphragm booster. So a common upgrade is a later model XJ master and booster, which requires moving the washer bottle and new brake lines, or another is a WJ, 99-04 grand Cherokee master and booster, which requires some modification to the firewall, and of course new brake lines. The newer XJ and WJ booster are both dual diaphragm booster so better braking, but the WJ one is for a 1000 pound heavier Jeep, so it is supposed to be the best upgrade. I’m doing the WJ upgrade, just waiting on a new prop valve to stop leaks.


Sent from my iPhone using Tapatalk

Thanks for the quick reply Azzi24. I'm familiar with the upgrade but would like to keep it factory. Thanks again