lastclodstanding

Guys I did a quick write up today on how I converted my 1989 Cherokee Limited from a junk ABS system to a decent power brake system for a member that emailed me. Figured I would post it up here incase it would help anyone else. If you have anything you think I need to add to it please let me know




Converting ABS brakes to a Power Brake System
Tested on a 1989 Cherokee Limited



One thing to remember most of all is the PV (proportioning valve) is important in swapping from ABS to power brakes. This is located under the MC (master cylinder). It is important to get this along with your new MC and Booster because the ABS PV is designed to operate differently from a traditional power brakes PV.

First off you need to find a good donor vehicle. I used an 88 or 90 model if I remember correctly. Mainly just make sure it’s coming from a Renix model XJ. Newer systems 92 + (I think) use a Chrysler system which is a ton better and can work with the older XJ’s but you have to change out the pedal assemblies. So if you go with a newer system remember to get the pedal also. Now if using an older Benix power brake system, it’s a direct drop in no problems.

Find a good donor vehicle, something with a complete system that’s not been left out to the elements. Make sure the lines are still attached to the PV or at least still in the vehicle (you will need them later). First off take the booster loose from brake pedal and then remove the 4 retaining nuts on the inside firewall. The booster and master cylinder are now loose from the firewall. Here is where your choice comes into play. Do you want to try and use the lines from the donor XJ or reuse the lines from the ABS system? I reused the lines from the ABS system. Reusing the lines from the ABS system requires you to use different ends. So if the lines are attached to the PV leave them. I took a small pair of cutting pliers and cut the lines loose from the PV. This will leave you the brake line ends you need. Be sure to remember where the lines went to and from what.

On to the XJ you are fixing. Removing the ABS MC and PV is simple and straightforward as removing the donor XJ’s MC, Booster, and PV. There are several connections on the ABS MC that you need to take loose. Take your time and look closely at them. Only one of your electrical connections will be reused and it’s obvious.

The unused connection will be taped up and tucked out of the way. Removing the ABS pump isn’t difficult but the lines are tough. The small flexible line comes out fairly easy but the hard line doesn’t. I end up cutting the line in two to get it out. Take your time and tidy up behind yourself as you go.

Before you install the new MC, booster, and PV you will have to address the break lines. If you took the entire lines from the donor XJ then you will have to work out getting them into place. It won’t be really hard, just take your time and work around everything. Now if you did like I did and decided to reuse your existing lines the fun begins. Begin by taking a compact tubing cutter and cut the lines just below the existing ends. After doing this you are left with 3 lines. Front driver, front passenger and rear. Remember earlier when I said “be sure to remember where the lines went to and from what”, this is going to make life so much easier for you. If you swap the passenger and drivers side around it’s not a big deal, but you don’t wont to get the rear port mixed up with either fronts. If you do one of the calipers wont get enough pressure and your rear will get way too much and possibly blow the wheel cylinders. Once you get your lines figured out and traced, put the appropriate line ends on the correct lines to match up to your new PV. It’s much easier now to go ahead and flare the lines and before you bend them. Now you can do a single flare or a double flare. I did a single flare because that is what the tool I had was capable of. A double seals much better and isn’t too much more difficult. With the new ends on and the tubing flared go ahead and bend your lines to form with a tubing bender. If you are really good you can bend them by hand, but use a bender anyway. Benders are cheap and good insurance.

With the lines bent to form and as close to the PV as possible begin installing the new MC, booster and PV. The assembly slides right back into place like the original ABS MC (which I believe was designed by some mad scientist who had a grudge against XJ’s). Now that the new unit is slid into place fasten it to the firewall with the 4 nuts you removed earlier and then refasten the booster to the brake pedal. Now time for the fun part getting the new lines attached to the PV. For me the first 2 went in like butter but that darn last one took me almost an hour. The lines are fine threaded and have to be perfectly lined up to thread into place. So after some blood and cursing you have the system totally hooked up. Now onto the bleeding of the system

Just like most brake systems it helps to bench bleed a new MC but its not necessary. With the fluid reservoir filled up have a friend start pumping the brake pedal. Pump it about 4 times and hold. Then with the pedal still being held open the bleeding screw on the front of the PV. Do this several times until you get nothing put brake fluid coming out. After bleeding at the PV move on to the calipers. Same as with bleeding the PV take your time and get all the air out. If you have any doubts keep pumping and bleeding. Do the same for the rear make sure you get clean fresh fluid and no air pockets. Also be sure to never let the MC run out of brake fluid or you will have to start all over again.

Now just give everything a once over and make sure everything I attached back and secure. Put the wheels back on and test them out. Depending on how wore your rear drums are you may need to get them turned or replaced to get the rear drums working correctly. Hope this helps.

Take care,

Camaron

BlueXJ

Good job Cameron. Maybe Kyle will want to add this to the write-ups in the library.

lastclodstanding

Thanks man. I know I havent found a write up on the net anywhere and thought it would be good to have.

Kyle

Thanks for the submission, please note that writeups should be submitted into the subsection titled "technical article submission". I will move this thread and add it to our writeup database.

Thanks

lastclodstanding

Sorry Kyle, I missed it. Thanks man.

Kyle

Not a problem, Added

tomh

hey thanks for the instructions and they helped very much. question for you tho. when you were all said and done did you have a problem with the blinkers

Lets_Ride_all

I did the same thing and my brake pedal is a lot higher now......I have heard this is common but has anybody found a fix for this? I am thinking about modifying the pedal by adding a second hole to move pedal towards floor about 4-6 inches.

bigtuna

my daughter has a 91 laredo i robbed the booster and master cyl. and prop valve off of a 95 cherokee fit like a glove i didnt even have to turn the adj. rod the pin just fell into place and i put the clip on brakes are awesome now. exact same pedal location. i was dreading it, the chg. over but it went really well.

Disoriented Hillbilly

Subd.

Kramer

Thanks for this write it helped alot but the one thing that I don't agree with is you don't have to swap the PV proportioning valve they are the same part number from abs to none abs and after spending a lot of time looking for a non abs one and finally buying one they were identical you just have to pull the plugs out of the the abs proportioning valve. This was just my research and I have tried both in my jeep and the both work the same if I am wrong Im sorry but I just want to help out other that were like me that almost stopes this mod due to not being able to find a proportioning valve or wanting to spend 50 on a new one thank you for your time

Dave A.

I read this in another thread reply from CAPTAINWOOT about the conversion and thought you might want to include with your GREAT write up, as the high pressure in the ABS can be very hazardous to anyone working on the system and unaware.
Thanks for for your writeup!

To depressurize the "ABS"system, key off pump the brake pedal untill it is hard (manual say fifty times). Then go ahead and do your swap, I would make all new lines in a case like this, then when you are done you know exactly what you have....
Good luck!

Brett Saltus

I have a 91 cherokee laredo with the bedix and found a 95 xj as a donor to upgrade to power brakes. The booster rod was a perfect fit and the whole swap wasn't too difficult. I bled the brakes and have decent braking pressure now, but could be better I think. My problem now is, I am hearing what sounds like a vaccum leak from the booster. It makes a constant "swooshing" sound, like wind. But the sound stops when I apply pressure to the brakes. Anyone have this issue or know what could be causing it?

dave1123

Yeah, I do. Internal seal in the booster where the pedal rod goes thru. Often times they will leak until used, other times they will leak only on heavy pedal pressure. Replacing the seal requires disassembly of the booster. NOT for the average person to do.

Brett Saltus

Thanks for your reply. I ended up putting a few spacers on the firewall to better align the booster rod with the pedal. About 1/3 in... I only put spacers on the top two bolts to angle the rod upwards towards the pedal. This seems to have fixed the issue because I can't hear that leaking sound anymore. Hope this works!