1994 Jeep Cherokee XJ - Page 3 - Mopar Forums
 


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Old 02-22-2017, 10:50 AM   #61  
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Wanted to get more braking ability. Accomplished that with a dual diaphragm booster and high pressure master cylinder. Firewall needed to be massaged to fit. At the same time we also eliminated the rest of the ABS to make room for an air compressor. Picked up a proportioning valve off a Cherokee without ABS which gives us 3 outlet ports instead of 2. The T for the front brakes was previously done at ABS unit, which is being eliminated. Replaced the spring in prop valve with a 4 wheel disk ZJ spring. There is definitely an increase in braking but it seems under heavy braking the pads and calipers are doing what they can. At 10 mph in dirt, front tires lock up and rears almost do.
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1994 Jeep Cherokee XJ-brake-booster-upgrade-001-640x480-.jpg   1994 Jeep Cherokee XJ-brake-booster-upgrade-003-640x480-.jpg   1994 Jeep Cherokee XJ-brake-booster-upgrade-005-640x480-.jpg   1994 Jeep Cherokee XJ-brake-booster-upgrade-010-640x480-.jpg   1994 Jeep Cherokee XJ-brake-booster-install-003-640x480-.jpg  

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Old 02-23-2017, 01:39 PM   #62  
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Sounds like it's coming together nicely...
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Old 03-04-2017, 07:29 AM   #63  
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Kinda. I installed this back in September, got frustrated and busy and set it aside. Wheeling season is around the corner so I got to get it going. I have a hard brake pedal like the booster is still not working. Have correct tool to test my booster vacuum now so hopefully will make some progress today.
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Old 03-04-2017, 07:12 PM   #64  
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Sooo. We go wheeling in the snow in Iowa, you waiting for summer?
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Old 03-04-2017, 08:28 PM   #65  
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We do some winter wheeling but it gets old running the same trails over and over again. Most trails are snow packed right now with anywhere from 8-15 ft of snow, not much fun to winch through the whole day. Here is a video of a snow run a few years ago when we had considerable less snow pack. Was a 15 hour day and we hit the deeper stuff after it started to get dark so not on video when the winch fest took over. After a few trucks pass through the snow trails begins to ice up. If you notice when coming back down the hill it is all slide and minimal control without letting off brakes, especially for my brother in the blue XJ.

Today I found booster is good, check valve is good, vacuum is only 13 hg. I will have to follow up on why vacuum is low, repaired only 2 leaks I found. I am going to JY tomorrow and pulling vacuum pump from an Audi to run brake booster. Also have a check valve with 2 ports on it so I can tie into engine vacuum later if I choose. Hopefully boosting my vacuum to 20 will get me where I want to be...or stop me when I want to anyway. Only symptom I am getting is running a little rich, idle is still good and engine running decent.
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Old 03-05-2017, 08:52 PM   #66  
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Got pump installed today with relay. Pumps down to 21 hg now to brake booster. Plugged engine vacuum port for testing. Could not locate vacuum switch locally but got an adjustable one ordered. Until it arrives I have booster back on engine vacuum. I left toggle switch on pump and tied it into booster with additional check valve. If I need emergency braking I can flip the switch, otherwise I have adequate braking for normal driving. Tested system using toggle switch today. Am able to lock up front brakes at 35 mph on dry pavement and getting good drag from rear. When switch arrives will clean things up a bit and melt down the heat shrink tubing on all wires. Am going to add a vacuum canister to help reduce pump cycling. Pretty bummed because I lost the space I had made for an air compressor but things can be re-evaluated when I get the compressor.
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Old 02-07-2018, 05:56 AM   #67  
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Oops I guess I forgot to update that I got my switch for the vacuum pump and it works good. Have now disconnected the wiring for it and hooked vacuum back to engine to see how truck performs with new brakes. Decided to try a set of powerstop pads and rotors. Found the battery dead when trying to move it over to do brakes. Had a lot of corrosion that I cleaned up while cussing myself out for the way things are wired up. Still didn't start. Put it on a charger and left it to return and find it still no good. Time to replace the battery, in my fashion. Over the years adding accessories to the truck I had a horrible stack of connectors on the battery and also had been putting off an electrical upgrade to the stock wiring in the truck, more about that later when I get it done. Replaced battery and only reconnected essentials to move over and complete brakes. Smooth enough and straight forward, I am looking forward to seeing the results. Now the fun stuff, we pulled out all the extra wiring I have installed in the truck. There was 40 ft of 2g wire, 25 ft of 4g and a ridiculous amount of 14 and 16g. Still a little left under dash which will be reused. Found a metal bracket that will work for a junction block at battery terminal. I need to drill and thread a few holes and it will be ready. Unfortunately schedules and weather are making progress slow, hope to be done in next couple weeks. Going to rerun my wire more efficiently and actually add back in a few things I had removed. I have a new switch panel to locate a mounting spot for as well as a new fuse block. Not much to show except this little sneak peak.
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Old 02-07-2018, 07:38 AM   #68  
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Looking Good.
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Old 04-19-2018, 03:07 AM   #69  
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Been busy with life and electrical has been slow to get done. Made some progress but have a lot of tidying up to do. Made some improvements to factory wiring and set up a secondary system for all add ons. The ground wire from battery to chassis was way undersized and was replaced. The power wire from battery to under hood fuse panel was undersized and was replaced. The wiring for the alternator runs through fuse in under hood panel. This wire was left in place as is and a duplicate wire was run through a fuse in parallel for more flow between alternator and battery. This will all aid in high load conditions such as winching. Power was run through a fuse to new fuse panel in kick panel of driver side. There it junctions and runs back to power inverter where it junctions to run to stereo amp. I have made drawings of this and will post later. I have tested power inverter with pole saw. It handles amps easily without dipping voltage. Should be able to easily run electric chainsaw if needed for trail cleaning as well as my electric impact.
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Old 05-05-2018, 07:20 AM   #70  
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As you already know we have been chasing a gremlin in my brakes. I ordered a gauge and checked my caliper pressures. We found 500 psi at rear and 1,000 psi at the front. We compared to brothers XJ and found same numbers. Due to booster and MC in my truck I figured it should be higher but moved on. We were unable to connect gauge directly to MC so we started to guess a little again. Jacked the back of truck enough to level MC and "bench" bleed it. Pushing pedal slowly like we normally do trying to not make a mess resulted in no air bubbles. A couple more hearty pushes found quite a bit of air, added in a few taps with a wrench and we eventually got all air removed, I hope. Sweet, one issue resolved but the way it was driving before told me we had another issue. Opted to order a new prop valve designed for disk brake conversion. I never did like the lines we installed between MC and prop valve so we made new ones. When removing prop valve we found a couple adapter fittings we had used. Here is where I believe we found our gremlin. One adapter was on front inlet of prop valve other rear output. When looking at the bore of fitting it is too small to fit a paperclip through. Got late last night so we have to snug down fittings and bleed system. Ended up using only 1 adapter fitting for the rear output of prop valve and we made sure it was proper bore. Front output lines fit perfect and we flared the correct fittings between MC and prop valve. After we get it snugged down and bled I will retake pressure readings. I suspect the air in MC is what allowed pedal to move, then the restriction is why pedal was so hard when it engaged. The lack of volume due to restriction could not move caliper pistons enough to truly grab. First picture is a fitting next to a piece of 3/16" brake line.
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1994 Jeep Cherokee XJ-20180504_213553_resized.jpg   1994 Jeep Cherokee XJ-prop-valve-box.jpg   1994 Jeep Cherokee XJ-prop-valve-1.jpg   1994 Jeep Cherokee XJ-prop-valve.jpg  
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Old 05-05-2018, 12:36 PM   #71  
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Challenging to say the least...
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Old 05-06-2018, 06:08 AM   #72  
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Got the air out of the lines and checked caliper pressure again. Front calipers did not change a lot in pressure as expected. Under heavy braking I am getting about 1250 psi now. Prop valve did help the rear brakes a lot though, am now getting 900 psi at heavy braking. To sum it up I went from a total 3,000 psi at all 4 wheels to 4,300 between eliminating restriction and changing valve. Took for a test drive and I successfully have brakes I am comfortable driving with. Won't lock up any tires but will stop safely. I feel confident in saying that changing the spring from a ZJ in the prop valve does not work properly. The distribution was the same as stock at 50% reduction to rear. I would recommend anyone doing a disk brake upgrade to purchase the new prop valve, it is only $50 and produces real results.
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