Okay, what on earth is this?

So tonight I break out the drop light and some tools and prepare for the wonderful task of replacing the brake shoes on this old '86 MJ.

I get the wheel off and as I'm being disgusted by the shape of the rear brakes (they look like those undersea pics of the Titanic. All rusty, and corroded. They look kinda organic in shape. Maybe this truck has been in the water before... ) and I spy this curious looking device. I can't find it in the Haynes manual. I ran outta time so I didn't get a chance to trace the lines.

So what the heck is this:


It looks like some sort of proportioning valve, but there looks to be one line going in and one coming out. And I have no idea what that arm with the little ball(as in teeny ball joint?) on the end of it would be for.

I'm sure I'll feel stupid when someone tells me what it is, but right now I'm perplexed.

Just guessing here but don't trucks need a bias change in brakes when they have heavy loads or light loads in them ?? Give us some more hints

That just compensates for bed load.

The more that's in the bed weight wise the harder the back brakes will work. PM eagle he's all over it

You guys rock!

A guy goes into the kitchen for milk and cookies...:shocked: uh, I mean beer and some beef jerky *cough* and you've already got it figured out.

I thought it was something like that, but since it's disconnected I couldn't figure out how it worked.

Yup, its a vehicle height(load) sensing proportioning valve. The little ball on the end of the lever connects to a bracket on the axle/diff cover.

I asked about about this about 8 months ago when I did an axle swap on a buddy's MJ (to 8.25)

You can try to mess with it, but it was just a whole lot easier to just Zip tie it up and enjoy.

John

That'll work. I like simple fixes that let me enjoy my MJ more often.
The only problem is that the more I fix, the more I learn is dangerously wrong with this goofy machine.:roll:
And I still love it!

So here's the question...will tying this thing up outta the way change the way my brakes feel? With that arm hanging down like that, did it in effect reduce the amount of braking force to the drums?

Or does it actually matter all that much?

SilverMJ said:

That'll work. I like simple fixes that let me enjoy my MJ more often.
The only problem is that the more I fix, the more I learn is dangerously wrong with this goofy machine.:roll:
And I still love it!

So here's the question...will tying this thing up outta the way change the way my brakes feel? With that arm hanging down like that, did it in effect reduce the amount of braking force to the drums?

Or does it actually matter all that much?

Click to expand...

If the thing is functional, tying it up will affect your braking. The one on my '88 MJ is tied up. I had to do a panic stop yesterday and locked up all four tires -- with 31s. My '88 XJ won't lock up any wheels even with stock tires. If yours is hanging down, you probably have no functional rear brakes.

I encourage you to replace those rusty lines. That's what blew on mine when I pulled that panic stop yesterday -- the hard line that runs along the frame rail above the gas tank. (Naturally it can't be anywhere that's easy to access.) FWIW -- an unloaded MJ shortbed on 31s stops pretty well with just front brakes.
:explosion

Well, no braking pressure in the rear would explain why the wheel cylinders look like the wreck of the Edmund Fitzgerald. They prob'ly haven't even been activated in ages. No telling how long it's been like that.
I'm gonna pick up new wheel cylinders tonight. They're $9 for the whole assy at Autozone.

I wonder how much the steel lines are and if they'll fit in my Focus... How long are they?

Go on, laugh. I get 33MPG! It's $13 a week for the work commute as opposed to the $65 in the Ram.

Even tho I'd rather drive the MJ. And I WILL, once I've done more repairs on it.:repair:

So Eagle, where do I sign up for the MJ Preservation Society?:clap:

use a cherokee prop valve and throw that load sensitive bullshit away.

personally, I like actually being able to bleed my brakes and get a firm pedal. the SLIGHTEST little particle getting in the brakelines will screw that valve up BAD.

less parts = less stuff to malfunction when you REALLY need it.

I just ended up removing the whole thing altogether, while attempting to repair the second brake line failure on my MJ. Like Eagle said, they tend to blow out along the framerail above/behind the fuel tank. Be warned, if you start trying to replace components back there, one thing may lead to another, because of the age/condition of those hard lines. I doubt you'll be able to find that line pre-bent anywhere, so you're better off getting some various lengths of 3/16" brake line and replace it all. In my case, I ended up removing that valve altogether and running a single line to the rears from the prop valve in front back. You have to cap the outlet for the return line on the prop valve (the front one on the bottom).
Ain't old rusty MJ's cool?
Jeff (preserving an '87MJ)

SilverMJ said:

So Eagle, where do I sign up for the MJ Preservation Society?:clap:

Click to expand...

Sounds like you just did party1:

Hooboy! I didn't think I'd get into all this. I just wanted to replace the pads and shoes.

What fun. So I buy straight lines and bend them with...what? Is there a small tubing bender available (CHEAPLY!!!) so I don't crimp/crush the tubing?

I like the idea of eliminating the extra valve. I REALLY like simple. As you said, less to break. I'm still trying to figure out how to eliminate all the electronic crap under the hood without losing my TB setup. :banghead:

As for a Rusty MJ, the drums are the first real rust I"ve found. The body's got some surface rust from scratches and dents, but nothing perforating. I think there might be some from where the clutch master cylinder leaked where the firewall meets the floor, but it may have simply bubbled the paint. I haven't checked closely yet.

I get overwhelmed with all that seems to be wrong with it. I'm not sure what, if anything can be kept from the steering/suspension setup. Then I remember I don't know enough about it, and it might not be all that bad.

And, of course, I remember that, so far, I've put less than $100 in it!

SilverMJ said:

As for a Rusty MJ, the drums are the first real rust I"ve found. The body's got some surface rust from scratches and dents, but nothing perforating. I think there might be some from where the clutch master cylinder leaked where the firewall meets the floor, but it may have simply bubbled the paint. I haven't checked closely yet.

Click to expand...

get on that floor rust ASAP!!!!



dealing with that is NOT FUN!!!

Rust hath many hiding places on an MJ

Lucky you have metal left in your d/s floorboard, Cheap..(although rusty!) Mine was gone from the framerail to the trans hump, and from the pedals to about halfway under the bench seat :bawl: I'm in the process of redoing the whole thing right now-I agree, NOT FUN!
Silver, you can get a cheap, hand-held tubing bender for a few bucks that'll work fine. I suggest you practice a few bends on some spare line so you can get used to working with it (you'll know what I mean when you start). You can get the brakelines already flared w/ fittings already on them that come in different lengths, but you'll probably end up having to cut one or more to length and re-flare the end. Spend a few bucks and get a decent flaring kit (double-flare variety), and remember to slide the fitting over the line after you cut it but BEFORE you flare the end. May seem like a no-brainer, but just wanted to remind you.
You can, like CheapXJ said, replace the MJ prop valve with an XJ one that doesn't have the extra return line fitting in it. If you do swap the prop valve, go ahead and pull out the airbox and washer fluid resivoir to free up more room to work. (You may find that the EGR line can get in the way too).
Good luck!
Jeff

You could always pull the bed off and do a really nice job and not have to work underneath it. That would let you replace any mounts that need it.
One thing always leads to another. Last year I needed to replace the seal on the downstairs toilet, that led to a replacing the flange which required cutting the big pipe in the cellar, etc. By the time I got done I was working pretty good with that PVC and wielding my sawzall like a pro....

I had mine tied up and disconnected for about 3 years. No problems whatsoever with the brakes. I could lock up all 4 in a panic stop with 33's. When I went to 35's my brakes sucked, but they were good enough for me. :firedevil

I re-did all my brake lines and took the opportunity to move the front proportioning valve to an easier-to-work-on location and eliminated the rear valve alltogether.
Jeep on!
--Pete

Here you can see where I mistakenly hooked up the rear line, then had to reroute it and plug the other one.

Then I ran a single line back to the rear axle. Everything seems to be working fine.

As you can see in this pic, I didn't even bother trying to match all the bends of the stock lines. Too much effort