WJ Grand Cherokee Master Cylinder and Booster Upgrade How-To

I'm working on upgrading my 88 XJ's master cylinder and single diaphragm power brake booster (NON ABS) to the newer and more powerful 2002 WJ master cylinder and dual diaphragm power brake booster.

This was my original source of information - http://www.4x4wire.com/jeep/tech/brakes/xj_wjbrakes03/booster/

I think I can make a better write-up.

What you need is a 1999-2004 Grand Cherokee WJ master cylinder and brake booster. Save the nuts that bolt the booster to the firewall and the lines that attach the to master cylinder. You also reuse the XJ pedal and brake light switch.

I got a used 2002 master cylinder and booster for $108 from Kubis Auto Parts in Auburn, NY (you can order from them online).

Remove the old master cylinder and booster by disconnecting the lines from master cylinder and removing the four bolts inside the passenger compartment on the firewall. Unbolt the one bolt holding the pedal and disconnect the brake light switch.



New on the left, old on the right...



New rod you have to modify...



Old rod...



I used a step drill to drill out the hole in the new rod until the bushings for the pedal bolt fit securely.



Next you have to grind the flat spot for the brake light switch. Old rod thickness measurement...



New rod thickness measurement before grinding and after drilling...



After grinding, an acceptable thickness IMO...



With the brake light switch on the new rod...



http://photos-e.ak.fbcdn.net/photos-ak-snc1/v2701/239/123/755350342/n755350342_6459292_3105412.jpg

Now for the brake lines...



For this you need a small pipe cutter and a brake line double-flaring tool kit. I got the pipe cutter at Sears and the double-flaring kit was a great deal at Advance Auto. The cutter even fits in the box with the flaring tools. There are some brake line adapters pictured but they weren't needed.

Cut the proportioning valve ends off of the lines coming from the master cylinder on both master cylinders. You're going to want to to put the nuts from the old lines onto the new lines because what will be on the WJ lines are metric and won't work with the XJ proportioning valve. So XJ nuts on the WJ lines (make sure you note the difference between front and back, and then make your double flares...





Then bolt it in...



It takes some creative bending of the lines to get them to work. Make sure not to bend any too much that you pinch a line. make gradual bends using a brake line bender or around pieces of pipe. Also, it is much easier to bolt the lines to the proportioning valve and then bolt them to the master cylinder since room is tight around the proportioning valve once the master cylinder and booster are in.

NOTE - Make sure to bend up the pinch seem above the booster so it clears the fender.

NOTE - Some people say you should use a 1/4" spacer between the booster and firewall for pedal position. I put some 1/8" thick washers on the bolts between the booster and firewall and the pedal position looks good to me.



http://photos-d.ak.fbcdn.net/photos-ak-snc1/v2701/239/123/755350342/n755350342_6459307_1097678.jpg

This was all done in about 3 hours last night (and the only light I had was flashlight and a gas lantern). Tonight, a lot of brake bleeding...

How is the pedal position?

thanks for the write up i like it more then the 4x4wire one that i was gunna use i so need stronger breaks its gettin scarys when you have to stop quick....which is one thing these out dated brakes dont do