If you have an ‘89 to ‘91 XJ Cherokee, you may have the problematic Bendix 9 Antilock Brake System. This ABS system was nationally recalled due to it being prone to failure. The Bendix system consists of a master cylinder, a motor/pump assembly, and 2 pressure accumulators. It is fairly simple to identify this system due to its lack of power brake booster that you would normally find behind the master cylinder on a normal power brake system.
Because the entire system is pressurized by an external pump, you must depressurize the system prior to removal. If this is not done, it can cause serious injury due to extreme pressure in the lines and accumulators. The system is easy to depressurize. Simply pump the brake pedal 25-40 times with the ignition switch in the off position.
Once the system is depressurized, you can proceed with the removal process. Start by disconnecting the brake lines from the master cylinder. Once the lines are free, remove the master cylinder from the firewall by the four bolts holding it in and disconnect the rod from the brake pedal. This can be difficult due to the position of the nuts under the dash, but a little patience goes a long way. Next, you must go back under the hood on the passenger side by the firewall. You will notice a black steel plate held on by several bolts. Under this plate resides the motor/pump assembly. Unplug and unbolt the assembly.
The accumulators are easily spotted as they look like mini air tanks. Remove the lines from the accumulators and pull them out as well. Once you have all the parts of the Bendix system removed, you are ready to re-install the “normal” power brake system.
You can use any brake booster and master cylinder combination for a Jeep Cherokee that you wish. My recommendation is to go with a booster from a ’95 or later because they are a dual diaphragm booster and give you a little better braking power. The booster bolts into the same 4 holes that you removed the Bendix master cylinder from. Then, the new master cylinder bolts onto the front of the booster like a normal setup.
You may need to do a little re-routing of brake lines to go from the master cylinder to the proportioning valve, but it’s pretty much the same setup. Two lines from the master cylinder go into the top of the prop valve, one line from the rear of the prop valve to the passenger side front caliper, lower front port on the prop valve to the front driver side caliper, and the lower rear port on the prop valve to the rear brakes.
There isn’t much information elsewhere that I have been able to turn up about this system aside from it being problematic. There really isn’t many pictures of the stuff floating around either. I did this conversion on my tuff truck by trial and error. I went through about 3 boosters and 5 master cylinders before I realized that all it took was a regular old Cherokee setup to swap right in.
If you have any questions or concerns on this conversion we encourage your to jump over the the Jeep Tech section of the forumHERE to discuss further.