murfanater

So i just found this out in my repair manual for my jeep comanche. The back breaks have not been working well and it turns out only the comanche has a device called 'Height sensing proportioning valve" What it does is sense when there is weight in the bed of the jeep or not. When there is it senses it and adds more break. This is to prevent it from locking up. But at the end of the paragraph is says that if vehicle is lifted that it can furnish the height sensing proportioning valve with a false reading.


So i def do not want to lower my truck. it is lifted only 2-3 inchs. What i need to know is why my back breaks arnt working at all. and alos is there something i can do before i say that it is the sensors fault. Ive seen lifted mj on the road and pretty sure they have back breaking plz tell me what i should do first to make sure i can get this working again. Its just the back breaks. the front work great. what should i do first.

Fsher21

I...have never heard of that before. Guess I learn something new every day. Back on topic though, have you even inspected the back brakes yet? First step if you haven't.

NoClearCoat

If it's lifted, the valve acts as there is no load. You need to extend the rod on the valve the EXACT amount of lift you have. If you extend it too much, It will act as if it has more weight than it does and the rear brakes will lock up (REALLY not good on a wet curve!!) so that's why I say EXACT lift. I wish you well, and get this fixed before you drive it on-road again. BTW where in GA?

murfanater

I live in fayetteville ga. And have u dont this? Would you have pictures?

mike mike

Looks like they remove them.

NoClearCoat

I was just wondering. I live in rockmart. Cherokees don't have that rear prop. valve and I know the MJs have them from the haynes manual. There has got to be some kind of adjustment procedure for a lifted truck but I honestly don't know. Cruiser 54 has an MJ and an XJ and several forum memberships (+ He knows what the f*** he's talking about) And maybe he can shed some light (or a link!) to your situation.. Wish you well...

rainandsun

did you bleed it properly at the time when u did the conversion.try bleeding the brakes first. its good to know that you don't need to replace anything, but my next guess if that doesn't work would be some seized pistons in your caliber. i did a rear disk brake conversion without having to change the prop valve, but there is no problem with my brakes not engaging.i figure as pulling the hand brake makes contact then to simply put it, hand brake is like a manual way to engage the rear brakes. hope im making sense to you, im not very good at explaining the concepts of how things work but you can look more online repair for and you can also have some to check for the repair estimates they gonna make if you go to a shop,. good luck

cruiser54

You have to extend the rod equal to the amount of lift. What size tires do you have? Obviously oversized, right?

With my Grandpa stock height MJ with 265/75/15 tires on aluminum wheels, I disconnected the rod and rotated the lever on the prop valve vertical and zip tied it into place.No rear wheel lockup or anything. YMMV.

BTW, it's BRAKES.