Brake's again

[lennyKatan]

Under the master cylinder is the combination valve.

I have four lines coming out of it. two of those lines are for the

front brakes.

The two that is for the back is the question I have.

Would it be a problem if those two lines don't go the same way

as they once did? non-abs

Also I notice somthing is missing....and thats the rear stabilizer

bar :cheers:

I have this comanche for about 5 years and never had any

problem with this. lucky hay :shake:

[Eagle]

MJs didn't have rear sway bars. You aren't missing anything.

 

The two lines from your front brake metering block serve different functions. Do NOT mix them up or you will create an unsafe condition.

 

Unless it has been modified, your MJ has a load (or height) sensing proportioning valve in the rear, above the rear differential. The primary brake line to the rear runs from the "nose" of the front metering block to the rear height-sensing (proportioning) valve, and then to the flex hose to the rear axle. Under normal conditions, rear brakes are always fed through this line so the rear brakes are proportioned to the load in the bed. More load --> lower height --> more brakes.

 

However, since when the truck isn't heavily loaded there isn't a lot of power going to the rear brakes, if you lose the front brakes you wouldn't have much reserve safety factor. So they built in a by-pass. That's the line coming out of the bottom of the front metering block. Normally it's blocked. If you lose pressure to the front brakes, a sliding valve in the metering block opens a different port and allows the fluid to go through the other line, which by-passes the rear height-sensing valve and thus provides full braking power to the rear wheels, regardless of how much or how little load is in the bed.

 

There have been several threads discussing why some of us advocate removing the rear proportioning valve and the by-pass line entirely, and setting the truck up so you always have full braking to the rear. That may or may not be a good solution for you. Whatever you do, do NOT change the arrangement of those two lines without understanding what you're doing. You could easily deactivate your rear brakes entirely.

 

This would not be "a good thing."

[lennyKatan]

That's a great reply, Thanks.

 

To make sure I understand your saying the line coming from the combination valve going to the rear is/should be the one coming from the nose or the valve end of the block. Correct?

That would then leave the line coming from the bottom of the block is the by-pass. This line should be the 1st line under the block, from the nose line (main line).

The next line / port is to the right / drivers side brake, that would leave the one on the other nose end would be to the front passenger side. Correct?

How would you check to see if this proporation valve works as it should?

Not by the nearest tree!

As you say "this would not be a good thing"

Thanks for your help

[Eagle]

The line that normally actuates the rear brakes is the one coming out the "nose" of the front metering block. There is no valve in there, so stop thinking of it that way ... you'll only get yourself in trouble expecting it to do something it doesn't do. The MJ metering block is entirely different from the XJ combination valve.

 

The only way I can think of to test the rear proportioning valve is to drive into some sand or pavement with a light coating of dirt on it, accelerate to maybe 15 or 20 MPH, slam on the brakes, and see if the rears lock.

 

Then disconnect the rod at the rear differential, push the lever on the valve up by the amount dropping the truck bed a couple of inches would move it, zip tie it in place, and repeat. If the proportioning valve is working, there should be a significant increase in rear brake lock-up the second pass.