badguru

I will see if I can find a big enough piece of plastic to machine a clear proporioning valve and use the stock shuttle.

It sure duz bleed it out. I just simulted a front brake failure by opening a front bleeder valve then I took the truck out and slammed the brakes on at around 30mph and got 2 perfect black marks from the rears skidding me to a stop. I closed the bleeder filled the mc back up gravity bled that caliper then took it back out and locked all 4 wheels with no problem all this with my bleeding technic. This brake system is the same as what's on a toyota hilux read up on that system and you understand how it works. And that line isn't just an emergency circuit it's opening every time you step on the brakes. And it's also being pushed back by fluid pressure from the front circuit and that makes it a (drumroll please) a proportioning valve how do you think it gets closed after u do that silly bleeding proceedure and you restore pressure to the fronts

Well maybe I don't know whom I'm talking to, but we can deal with that bromance later. Ghetto modifications to your brakes r not good The factory spent a lot of time and money desiging them, so when you kill a school bus load of children being driven by a nun, it goes from accident to murder. Aftermarket brake manufactures have liability on their products. This thread was to have a practical way to bleed ur brakes,and how the rear height sensing valve works. Like comanche afficianado said when that pressure reaches that plunger with the 2 orings it has no place to go well he is right and wrong. Pressure applied to a piston or in this case that plunger that piston or plunger will move (that's how ur engine works) which opens that other line to the braking system increasing overall volume to the rears. In this case the height sensing valve acts as a restricter. pressure remains constant but the hs valve uses volumn to move the plunger until the whole system reaches equilibrium. So depending on where the hs valve is at the time you hit you brake that will determine your overall braking force. That valve works in both direction say your unloaded and slam on the brake nose goes down @$$ end goes up more braking force it is also interactive it will change as you move the hs valve while braking because the orriface size changes as u move the leaver up or down. Remember if you apply 10 psi to a 1 square inch surface it will be half the force of if you apply it to a 2 square surface. Sorry if my writing is bad my keyboard autocorrect is defaulting to max and I cantget it to stay on my settings I'm having to rewrite dam near every word I type

Had to see it to believe it. I'm going to open up my front bleeders an see if I have good rear brake. If I do I'm sticking with my procedure. Let you know tomorrow.

My 89 base is an original untouched 83k truck I bought from the original owner and that brake line routing is backwards from the truck I know has original factory lines on it the line coming out the bottom goes to the height sensing valve and from the other side of the hsv to the t fitting. Good luck to anyone using that bled procedure if you have had the whole system drained like I did on my 89 eliminator when I replaced every part of the brake system except the prop valve. Anyway my brakes are bled. I also wish my mj had front leafs like the one in the picture.

That's great if you only drive around with no front brakes. In normal operation that's a signal line that determines how much braking force the rears should have sent to them. Stomping on ur brakes with the front bleeders open to bleed ur rears and having to go around and bleed everything several times to get it bled sound incredible to me. Please post that from ur fsm so I can check it out. Who knows I been wrong before. And I did study the pics closely and everything I see makes me think I'm right.

Your front and rear circuits are independent of each other so if u lose ur front you still have a sealed working rear circuit that will stop your truck. So why would you need an emergency bypass? At the back of your truck where you have that valve. It let's more or less volume of fluid past it depending on it's position. That moves that shuttle or prop valve in the block to give you more or less braking at the rear. The correct term for it is a servo spool just like in a backhoe or a farm tractor you know those oily hand leaver things with all the hoses coming out of them. This RETURN line gives that back pressure at the valve So it can shuttle under pressure to change the amount of volume to the rears. Its a loop system and in wrong to call it a return line. it's a Signal line back to the prop valve. So you have to bleed the air coming from the T-fitting throught the leveling valve back to the prop valve. Same setup on Toyota's and older chevy duallys. I used the same bleeding technic on all 3 of my jeeps and I can lock all 4 Tires and I have a real good petal. But please make a copy from your factory service manual and post it for me to look at. I'm always ready to keep a open mind.

Ok let's start from the top. When ur jeep was being built it came down an assembly line. At sum point a poor slob had about 2 minutes to make the final connections of the brake lines, fill the system, and bleed them. All in 2 minutes. So it can't be all that hard right well it's not hard at all. Lets look at the system. Master cyl has 2 lines coming out and going to the proportioning valve right? Right okay next the prop valve has only 3 lines coming out of it that's right only 3. 2 For the front calipers and 1 for the rear drums that's right only 1 for the rears. So what's that other line. That everyone likes to put a plug into? Its a (drumroll please) RETURN LINE. Why would u have 2 lines going to the same place? So after bleeding ur rears move up to the prop valve (big nut lower front) pump up the brakes like ur doing a wheel cyl and just crack the nut enough to let the air out. Repeat till fluid is running with no air. Please don't tell me that might leave air in the system because believe it or not (trademark Ripleys) you always have sum air in you brakes. Oxygen loves iron that's how ur truck got rusty. Thus ends today's lesson.