Jerry Posted October 18, 2011 Share Posted October 18, 2011 Hello all :waving: I'm doing some preliminary reading up on getting rid of the rear axle load sensor valve, please can any of you fellow Comanche nuts confirm/deny that this diagram (Thanks MrSimon :bowdown: ) is the correct and most simple set-up for removing the load sensing valve? And, what's the deal with the XJ front prop valve? I've read that if I don't put one of those in, rear brake lock-ups might become a problem. Is that correct and if so how bad is it? Does it make the truck un-drivable? I'd like to avoid the hassle/expense/time factor of swapping out yet more stuff if I can! Thanks in advance :wrench: Link to comment Share on other sites More sharing options...
Blue88Comanche Posted October 18, 2011 Share Posted October 18, 2011 if you are going to remove the MJ prop. valve to insert the plug then might as well drop in the XJ prop. my thing is why risk it, if it is known to lock up when it shouldn't and i know the solution i would do it. Link to comment Share on other sites More sharing options...
Jerry Posted October 18, 2011 Author Share Posted October 18, 2011 if you are going to remove the MJ prop. valve to insert the plug then might as well drop in the XJ prop. my thing is why risk it, if it is known to lock up when it shouldn't and i know the solution i would do it. Sounds like a fair assessment. So if I understand you right, the front proportioning valve must be removed anyways in order to blank off the lower front port? And if it's off anyways then ........... Is this an easy task? :cheers: Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 18, 2011 Share Posted October 18, 2011 Next on my list. Would I get an XJ prop valve at the junkyard or a parts store (i.e. are they available new?) Link to comment Share on other sites More sharing options...
Jerry Posted October 18, 2011 Author Share Posted October 18, 2011 Next on my list. Would I get an XJ prop valve at the junkyard or a parts store (i.e. are they available new?) :thumbsup: That was going to be my next question Link to comment Share on other sites More sharing options...
acfortier Posted October 18, 2011 Share Posted October 18, 2011 I don't believe you can get them new from the store, your best bet would be a junk yard. Link to comment Share on other sites More sharing options...
Eagle Posted October 18, 2011 Share Posted October 18, 2011 if you are going to remove the MJ prop. valve to insert the plug then might as well drop in the XJ prop. my thing is why risk it, if it is known to lock up when it shouldn't and i know the solution i would do it. But the XJ proportioning valve is well-known to gradually seize up and leave you with NO rear brakes. That's why a lot of XJers remove the O-ring and spring -- which is just making the proprtioning valve into something that works just like the MJ distributiuon block already works. It makes much more sense (IMHO) to keep the MJ front distribution block. If you find that the rear brakes often lock up prematurely (this has not been a problem for me), you can add a Wilwood adjustable proportioning valve to control that. Link to comment Share on other sites More sharing options...
Eagle Posted October 18, 2011 Share Posted October 18, 2011 So if I understand you right, the front proportioning valve must be removed anyways in order to blank off the lower front port? And if it's off anyways then ...........Is this an easy task? You do NOT have to remove it to block the lower front outlet port. Just unscrew the old tubing nut and screw in a plug. Done. Link to comment Share on other sites More sharing options...
Jerry Posted October 19, 2011 Author Share Posted October 19, 2011 Thanks for the info :thumbsup: My blue truck never had a load sensing valve since I got it and I've never had any lock up problems. On the other hand, my red truck still has one and I have tried the manually locking the load sensor arm in different position and it seems much more prone to locking up without a load on board :dunno: Weird! I thought I read somewhere that the XJ prop valve doesn't apply full pressure to the rears right away when you hit the pedal? Any more info on that anyone? Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 19, 2011 Share Posted October 19, 2011 You do NOT have th remove it to block the lower front outlet port. Just unscrew the old tubing nut and screw in a plug. Done. That sounds like a better plan. It looks tight but I'm sure you can get to it. Eagle, do you have a size? I had heard to use a trimmed down 1/2" fine thread with an o-ring on the bolt head...is that right? ...and does the brake fluid dribble out of the MC while it's un-capped? Link to comment Share on other sites More sharing options...
Eagle Posted October 19, 2011 Share Posted October 19, 2011 That sounds like a better plan. It looks tight but I'm sure you can get to it. Eagle, do you have a size? I had heard to use a trimmed down 1/2" fine thread with an o-ring on the bolt head...is that right? You probably read that in one of my posts -- that's what I did. ...and does the brake fluid dribble out of the MC while it's un-capped? Nope. Unless you had a front brake failure and the rear bypass got actuated, that circuit should not be under pressure. There is fluid in that line IF the proper bleeding method was used, so what's in the line will dribble out -- but it won't drain the MC. Link to comment Share on other sites More sharing options...
RDAN1 Posted October 19, 2011 Share Posted October 19, 2011 I thought I read somewhere that the XJ prop valve doesn't apply full pressure to the rears right away when you hit the pedal? Any more info on that anyone? I just pulled an XJ prop valve along with the MC and Booster from a 96 XJ to put in my MJ. Is the XJ prop valve "serviceable" or should it be "cleaned out" if I decide to install it ? any tips? Link to comment Share on other sites More sharing options...
Jerry Posted October 19, 2011 Author Share Posted October 19, 2011 I think this thread has slightly lost the thread :D In summary then: 1 - Get XJ Proportioning valve from wreckers, check/clean and blank off lower front port 2 - Remove MJ rear proportioning valve assembly and the brake lines that feed it(optional) 3 - Remove MJ front proportioning valve 4 - Install XJ front proportioning valve and re-connect brake lines 5 - Bleed system 6 - Test drive 7 - Drink beer and feel satisfied with another MJ upgrade successfully completed Please can someone confirm this is correct or edit as necessary? :wrench: The diagram below is correct but should show an XJ proportioning valve not the MJ one? Link to comment Share on other sites More sharing options...
Eagle Posted October 20, 2011 Share Posted October 20, 2011 In summary then: 1 - Get XJ Proportioning valve from wreckers, check/clean and blank off lower front port NO. On the XJ proportioning valve, the lower front is what feeds the rear brakes. 2 - Remove MJ rear proportioning valve assembly and the brake lines that feed it(optional) 3 - Remove MJ front proportioning valve 4 - Install XJ front proportioning valve and re-connect brake lines 5 - Bleed system 6 - Test drive 7 - Drink beer and feel satisfied with another MJ upgrade successfully completed Please can someone confirm this is correct or edit as necessary? :wrench: The diagram below is correct but should show an XJ proportioning valve not the MJ one? No again. The primary rear brake line on the MJ comes out the "nose" of the distribution block. The XJ proportioning valve has a plug in the nose that retains the plunger and spring. The rear brake line on the XJ goes to the lower front outlet that gets plugged on the MJ. Link to comment Share on other sites More sharing options...
acfortier Posted October 20, 2011 Share Posted October 20, 2011 There should be another diagram in the same thread you found that picture that has the XJ proportioning valve, but it is essentially the same, just one less port (in the back). Link to comment Share on other sites More sharing options...
Jerry Posted October 20, 2011 Author Share Posted October 20, 2011 OK, edited. Thanks Eagle :thumbsup: 1 - Get XJ Proportioning valve from wreckers and check/clean 2 - Remove MJ rear load sensing valve assembly and all the rear brake lines 3 - Remove MJ front proportioning valve 4 - Install XJ front proportioning valve and re-connect the front brake lines as before 5 - Install new brake line from lower front prop valve port to rear brakes 6 - Bleed system 7 - Test drive 8 - Drink beer and feel satisfied with another MJ upgrade successfully completed :wrench: Before: After: Credits again going to MrSimon :cheers: I'd like to get this spot on so this thread will be useful as a simplified cheat sheet for anyone doing this common mod. Once I've got it nailed and confirmed as correct I'll post a new thread with just the instructions and diagrams Thanks for the input guys :thumbsup: Link to comment Share on other sites More sharing options...
Jerry Posted October 21, 2011 Author Share Posted October 21, 2011 Bump :waving: Please can someone let me know if I got it right now? TIA :bowdown: Link to comment Share on other sites More sharing options...
Eagle Posted October 22, 2011 Share Posted October 22, 2011 Looks good from here. Disclaimer: To be candidly blunt, I still think putting an XJ proportioning valve into an MJ is about the dumbest thing you can do, but that's only because I've been driving my old XJ without any rear brakes for two or three years due to the bloody proportioning valve clogging up and me not having time to take it apart and deactivate the O-ring and plunger. Once I do that, it'll be just like an MJ distribution block -- no proportioning function at all, but at least I'll have rear brakes. I can deal with too much rear brakes a lot better than I can deal with NO rear brakes. Just to repeat myself, if using an XJ proportioning valve is such a great idea, why do so many XJ owners take the O-ring and spring out of it? Link to comment Share on other sites More sharing options...
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