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eliminating the MJ proportioning valve?

BrettM

BrettM

NAXJA Forum User
Location
michifornia
I'm nearly done with the 3 link, and one of the small things left is the brakes, and I'd like to just get rid of the load-sensing proportioning valve. I want to do this the easy way by keeping the 2 lines running to the rear so I don't have to mess with stuff all the way up to the master cylinder.

Here is what the factory setup is; can I just plug or reroute a line or two?




and while we're on the topic of brake lines, does anybody know a source for some good little tabs for attaching brake hard lines to a bare axle?
 
Just run the main line (with pressure}) to your rubber line. Thats what I did, the old line is still there, just not connected to anything.
 
I replaced the MJ prop valve and removed the extra line on the Drag MJ. But the previous poster says that you can just disconnect, so that works also. For brackets for the hard line; I used the threaded holes on top of the right side and just made a small luminum bracket. The left side is short and stays in place if bent properly
 
summitlt said:
Just run the main line (with pressure}) to your rubber line. Thats what I did, the old line is still there, just not connected to anything.
Click to expand...

Did the same as well, then later went back and removed the second line completely and capped the port on the prop valve under the MC (3/16" IIRC)
Jeff
propvalvebypass.jpg
 
I am about to do this as well, which line is the MAIN line? Can't you just tee both of those lines together (from the prop. valve) and run that to the rubber line?

Andy
 
I suppose you could.....the second line is actually a "safety" line that pressurizes in the event of a front brake circuit failure and sends full braking to the rears. It is normally not pressurized. It is the line that runs out of the bottom of the prop valve (the one toward the front, not the rear). The main line that supplies the rear comes out of the nose of the prop valve. Do a quick search on this topic or on user Pete M....he posted a nicely labeled pic of his prop valve on here a little while ago.
Jeff

edit: Here's the thread...
http://www.naxja.org/forum/showthread.php?t=60086
 
I donated one to Eagle to disect.....hopefully the results will be in soon as to...

1.) how it works....
2.) what would make a suitable replacement...
3.) can you bypass it safely without loosing all braking ability ?

Stay tuned....:D
 
I replaced the load sensing valve with a tee on my '87... now I can lock up the rear wheels. Whether that is good or not is your call.
 
I dont understand how the second line was for emergencys, the bottom line had no fluid in it when I pulled it, so that wouldnt help at all.

It can be removed, I did it, stops fine.
 
I just replaced the manifold at the master cylinder with one from an XJ and removed the prop. valve all together.
Done.
The XJ only has one line going to the rear axle.
 
i just finished my brakes on my xj, i have 3/4 ton brakes front and rear, i run one line to the rear, and one line to a "t" for the fronts, no valve, all 4 lock up at the same time
 
summitlt said:
I dont understand how the second line was for emergencys, the bottom line had no fluid in it when I pulled it, so that wouldnt help at all.

It can be removed, I did it, stops fine.
Click to expand...
Be careful.

The MJ FSM says that the second line is (as someone pointed out) a safety line. In the event of loss of the front brakes, rear braking is shifted to that second line and bypasses the load-sensing proportioning valve. As well as I can determine, if you block off that second port leading to the rear, in the event of losing the front brakes I believe you will have NO brakes.

Two solutions, both eliminating the rear load-sensing proportioning valve:

(1) As some have done, run both lines into a tee fitting somewhere downstream from the front combo valve, then run a single line from the tee to the rear axle flex hose; or

(2) Remove the MJ combo valve and replace with an XJ combo/proportioning valve, and run a single line from that the the rear flex hose.

I strongly advise against running with that second port blocked off.
 
Eagle said:
Be careful.

The MJ FSM says that the second line is (as someone pointed out) a safety line. In the event of loss of the front brakes, rear braking is shifted to that second line and bypasses the load-sensing proportioning valve. As well as I can determine, if you block off that second port leading to the rear, in the event of losing the front brakes I believe you will have NO brakes.

Two solutions, both eliminating the rear load-sensing proportioning valve:

(1) As some have done, run both lines into a tee fitting somewhere downstream from the front combo valve, then run a single line from the tee to the rear axle flex hose; or

(2) Remove the MJ combo valve and replace with an XJ combo/proportioning valve, and run a single line from that the the rear flex hose.

I strongly advise against running with that second port blocked off.
Click to expand...
thank you, considering I've lost front brakelines twice in the last 18 months (once on the street, once on the trail) I will not block off the second port.
 
Eagle said:
Be careful.

The MJ FSM says that the second line is (as someone pointed out) a safety line. In the event of loss of the front brakes, rear braking is shifted to that second line and bypasses the load-sensing proportioning valve. As well as I can determine, if you block off that second port leading to the rear, in the event of losing the front brakes I believe you will have NO brakes.

Two solutions, both eliminating the rear load-sensing proportioning valve:

(1) As some have done, run both lines into a tee fitting somewhere downstream from the front combo valve, then run a single line from the tee to the rear axle flex hose; or

(2) Remove the MJ combo valve and replace with an XJ combo/proportioning valve, and run a single line from that the the rear flex hose.

I strongly advise against running with that second port blocked off.
Click to expand...
just to clarify, your option 1 is this, correct:

 
Running both lines into a tee will mean you'll always have rear brakes, but as Lawn Cher notes -- the rear will be prone to locking up because an empty PU has very little weight over the rear axle. IMHO swapping in an XJ combo valve is a better solution, but the best would be to eliminate both the combo valve and the proportioning valve, and run a single line right from the master cylinder to the rear axle flex hose with a Wilwood adjustable proportioning valve in it. That way you can dial in the braking so it won't lock up, and still adjust for more bracking if you're going to tow or carry a heavy load.

But ... you would lose the brake system failure warning light switch, and that might not be legal. I assume most of us are sensitive enough to know instantly if we've lost half our brakes, but I wouldn't sell a vehicle with that feature disabled.
 
BrettM said:
just to clarify, your option 1 is this, correct:

Click to expand...
Correct.
 
On the xj they have a brake light that is pluged into the prop valve. Will that work with the mj if so you could put in an xj prop valve and run a single hard line back and eliminate all the double lines and t-fittings. simple = Better.
As Eagle state front's directly off the master rears to a wilwood style prop valve back to rear axle is my preferance too
 
Hijacked

BrettM said:
I'm nearly done with the 3 link, and one of the small things left is the brakes
Click to expand...

Well, if it's nearly done, WHAT THE HECK IS TAKING YOU SO LONG TO GET SOME PICS UP.

ha, saw a lot of good ideas in the design phase just want to see how they turned out for ya.

Hijack over
 
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