Whitaker717 Posted July 7, 2021 Share Posted July 7, 2021 Hi guys can someone recommend where I can get a portioning valve for my 87 Comanche. Disk in front and drums in rear. My guy is having some brake issues with the Comanche and I’m not sure what he is talking about. He said I need a new portioning valve. What kind do I need to buy? Thanks Link to comment Share on other sites More sharing options...
Pete M Posted July 7, 2021 Share Posted July 7, 2021 the system is complicated and I'm scared about what your guy thinks may be going on since it is sooooo different than normal cars. the thing up front that looks like a prop valve isn't a prop valve. it is just a combination valve (which is not available new). MJs have a rear height-sensing proportioning valve (which is also no longer available new). is he having difficulty bleeding the system? the link in my signature has the factory bleeding procedure in it. Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 7, 2021 Author Share Posted July 7, 2021 I think your right Pete. You have a picture of what he needs to buy. Link to comment Share on other sites More sharing options...
Pete M Posted July 7, 2021 Share Posted July 7, 2021 and the rear arm needs to be in a relatively horizontal position which could mean unhooking it and holding it up with a ziptie if the truck is on a lift. new parts aren't available. and they rarely fail. the vast magoirty of the time it's "operator error". here's an interior shot of the front piece, XJ vs MJ. and this yellow is the correct position for the rear arm. note that the arm is in the wrong position (due to the truck being put on a lift and let down without correction. ) Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 7, 2021 Author Share Posted July 7, 2021 This might be a silly question but how do you fix this? If I bought one of these would it help fix it or should I just have him take it to a dealership. I’m wondering if the previous owner removed something. Link to comment Share on other sites More sharing options...
Pete M Posted July 7, 2021 Share Posted July 7, 2021 what precisely needs to be fixed? what is the problem that your guy is experiencing? have you found the factory bleeding procedure yet? does your truck still have the rear valve at all? and no, you can't just shove an XJ unit in place of the MJ part without doing other things too. they are not the same device and don't do the same job, even though they may look similar. the XJ prop valve is an actual prop valve and controls the power split between the fronts and rears. the MJ unit simply... sits there. it's sole purpose is to wait for a brake failure and then the little shuttle moves and gives full power to the rear brakes (bypassing the rear height-sensing valve by the rear axle) new MJ parts are not available. but they are rarely the actual problem. find out what your guy is doing. Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 7, 2021 Author Share Posted July 7, 2021 Thanks Pete. It’s hard for me to find out what he is doing when I don’t know. Haha. I know the part from above has been removed for some reason so I need a replacement from somewhere. He was trying to put a Cavalier Prop valve in it I believe. I’m not sure what to do at this point. That’s the only thing keeping me from getting the Comanche back. Link to comment Share on other sites More sharing options...
Pete M Posted July 7, 2021 Share Posted July 7, 2021 find out what got him to this point. was it just a problem bleeding the system? Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 7, 2021 Author Share Posted July 7, 2021 I believe that’s the only problem. It started by the Comanche pulling real hard to the left. Found out a caliper was bad so he replaced both front calipers, rotors and pads. Tried bleeding the system and has had issues ever since. I believe. Let me ask you this Pete, will a Jeep dealership be able to fix it? Or is it too old? Link to comment Share on other sites More sharing options...
Pete M Posted July 7, 2021 Share Posted July 7, 2021 he must bleed the system via the factory method. regular bleeding will never get the air out of the emergency line. Link to comment Share on other sites More sharing options...
JMO413 Posted July 7, 2021 Share Posted July 7, 2021 44 minutes ago, Whitaker717 said: I believe that’s the only problem. It started by the Comanche pulling real hard to the left. Found out a caliper was bad so he replaced both front calipers, rotors and pads. Tried bleeding the system and has had issues ever since. I believe. Let me ask you this Pete, will a Jeep dealership be able to fix it? Or is it too old? As someone who works at a dealership. Most will have no idea how to work on your truck. Unless they have a very seasoned tech. We had a MJ at our dealership and I had to help the tech work on it. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 7, 2021 Share Posted July 7, 2021 52 minutes ago, Whitaker717 said: Jeep dealership be able to fix it? Or is it too old? If you know of a reputable dealer that has been around since the time of the MJ, you might end up with someone competent enough to bleed the system the factory way. Same as JMO, I work at a dealer as well and only a few of the techs remember the MJ and the AMC|Jeep days. And they are quickly retiring. Link to comment Share on other sites More sharing options...
JMO413 Posted July 7, 2021 Share Posted July 7, 2021 Just now, eaglescout526 said: If you know of a reputable dealer that has been around since the time of the MJ, you might end up with someone competent enough to bleed the system the factory way. Same as JMO, I work at a dealer as well and only a few of the techs remember the MJ and the AMC|Jeep days. And they are quickly retiring. All ours from that era have retired. We still have 1 GM guy that can actually rebuild a carb but he's retiring here shortly. Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 8, 2021 Author Share Posted July 8, 2021 Oh man don’t tell me that. I’m not sure what to do. I doubt my guy has any idea how to do that. Any suggestions? Lol Link to comment Share on other sites More sharing options...
Pete M Posted July 8, 2021 Share Posted July 8, 2021 FOLLOW THE INSTRUCTIONS IN THE LINK I GAVE YOU. print them out and hand it to him. there's just one extra step in order to get the air out of the emergency line. he can handle it, but only if he knows about it. Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 8, 2021 Author Share Posted July 8, 2021 Is that the one from 05mx Pete? Link to comment Share on other sites More sharing options...
Pete M Posted July 8, 2021 Share Posted July 8, 2021 Quote After bleeding the brake calipers and cylinders the rear brake by-pass line must also be bled. Open a front caliper bleed fitting and depress the brake pedal to the floor. This will shuttle the by-pass differential valve and allow fluid to flow through the by-pass line. The brake warning light on the instrument panel will illuminate when the ignition key is in the ON position. This signals the shuttling of the valve. Re-Bleed the rear brake cylinders with the front caliper bleed fitting open. After re-bleeding the rear brake cylinders the entire system must be bled again. Bleed the brake calipers and cylinders in the following sequence: 1st -- Right rear 2nd -- Left rear 3rd -- Right front 4th -- Left front Link to comment Share on other sites More sharing options...
jeepmjga Posted July 8, 2021 Share Posted July 8, 2021 Look at the procedure Pete has posted. Sounds like that is probably the issue. Also make sure he has the calipers on the right side. The bleed screw and banjo fitting should both be on the top of the caliper (speaking from experience here). If the brakes still will not bleed after performing the CORRECT procedure for the height sensing valve you could try eliminating it and replacing the shuttle valve with a proportioning valve from Wilwood or some other brand. However if you do go this route make note that you will need to adjust the valve manually if you are carrying a heavy load in the bed. Link to comment Share on other sites More sharing options...
Eagle Posted July 10, 2021 Share Posted July 10, 2021 On 7/7/2021 at 5:10 PM, Whitaker717 said: This might be a silly question but how do you fix this? If I bought one of these would it help fix it or should I just have him take it to a dealership. I’m wondering if the previous owner removed something. No. That's a proportioning valve for an XJ Cherokee or a ZJ Grand Cherokee. Look again at the photo Pete posted showing the XJ and MJ units. That thingie in the front of the Comanche is NOT a proportioning valve, it is a distribution block and brake failure warning light switch. That's ALL it is. Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 10, 2021 Author Share Posted July 10, 2021 So it seems that the rear thing has been bypassed somehow. It’s not on my truck. (The second picture of Pete’s post) I think my guy has it figured out now but who knows. I just don’t know enough about this system. Pete has been really helpful and patient trying to educate me on it. Link to comment Share on other sites More sharing options...
Eagle Posted July 10, 2021 Share Posted July 10, 2021 Quote I know the part from above has been removed for some reason so I need a replacement from somewhere. Which part has been removed -- the front distribution block, or the rear proportioning valve? If the front distribution block has been removed, how did you drive the truck before you took it to the shop? If the mechanic removed it -- tell him to put it back in, and then find a different shop. If the rear thing has been eliminated, you don't have a proportioning valve (unless the front distribution block has been replaced by an XJ or ZJ front proportioning valve. My advice is to buy an aftermarket adjustable proportioning valve and install that in the line to your rear brakes. That will allow you to tune your brakes to avoid premature rear wheel lock-up (which is the purpose of proportioning valves). However, as I think someone already mentioned, if you tune it with the bed empty, you should readjust it if/when you carry heavy loads. If you tune it with a heavy load, you MUST readjust it when you run empty. https://www.wilwood.com/MasterCylinders/MasterCylinderProd?itemno=260-10922 From the factory, the MJ had TWO hard lines from the front to the back. One fed the rear proportioning valve, and that was the primary, everyday brake circuit. The other line was an emergency by-pass line. If the front brake circuit fails, you want full pressure to the rear brakes, so the emergency circuit by-passes the rear proportioning valve to deliver full pressure to the rear brakes. After re-reading this entire thread, I'm still not clear what was removed from your truck, or what "problem" your mechanic was having. And did HE remove something, or was something removed by a previous owner? Link to comment Share on other sites More sharing options...
Whitaker717 Posted July 10, 2021 Author Share Posted July 10, 2021 It seems the previous owner removed the rear portion valve. My guy had to replace my front calipers and rotors and pads. Tried bleeding the system and was having a tough time. That’s about all I know as of now Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now