Positioning the brake pressure differential valve

[crlang2]

Hello Comanche Club,

 

This is my first post... My son and I bought a badly rusted 91 Eliminator a few years ago and the first thing that happened was the rear brake lines blew out.

 

As we got into the project we overhauled the entire drive train and rather than try to rehabilitate the rear drum brakes (rust piles) we installed the Teraflex rear disk kit. Also, we put in stainless brake lines.

 

Things are back together and we are trying to continue using the rear axle proportioning valve. We have read the posts by Eagle and others about bleeding, but we appear to be having trouble with the position of the differential valve under the MC.

 

We have previously bled all the brakes in whatever the current position of the valve is. The brake warning light is on, so it is not centered. I suspect that it got rammed forward when the rear brake lines blew and has been there ever since. Using the FSM procedure quoted by Eagle, we opened a front caliper bleed screw and depressed the brake.

 

My understanding is that this should drive the differential valve to the rear, as though the front brakes have failed, permitting the "backup" rear line to be bled. Should I have heard the valve move? Or should the brake warning light have turned off and then on as the valve moved to the other extreme? I have a feeling that it didn't move, perhaps more pressure (alot more) is needed on the pedal, but since the rear lines are not fully bled, the pedal is soft and goes to the floor (unless pumped).

 

We went ahead and bled the rear brakes with the front caliper open, but did not get any air out of the line(s).

 

Does anyone have any experience with what it takes to move the differential valve position? Particularly when there is air in the rear lines?

 

Thanks in advance,

 

crlang2

91 Elminator

86 Comanche Custom

[Eagle]

After the second time my rear brakes blew out, I replaced the entire hard line all the way from the front distribution block (combo valve, which isn't really a combo valve in an MJ) to the rear flex hose. The brake warning light was on when I finished and all the bleeeding in the world wouldn't make it go off -- which had never happened before.

 

Finally, one day with the engine OFF, so I had no vacuum assist, I just stomped on the brake peddle as hard as I could. When I started it up, the brake light was off.

[watchamakalit]

According to my haynes manual that is the proper proceedure to reset the valve. Stop the SH@T out of the pedal without the motor running(ie:not vacuum assist)

[summerinmaine]

Finally, one day with the engine OFF, so I had no vacuum assist, I just stomped on the brake peddle as hard as I could. When I started it up, the brake light was off.

 

Of course, that simply follows the time-honored principle:

 

Nolite id cogere, cape malleum majorem

 

I know there's a formal translation, but I always like to think of it as:

 

"If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer. ... "

[Eagle]

Of course, that simply follows the time-honored principle:

 

Nolite id cogere, cape malleum majorem

 

I know there's a formal translation, but I always like to think of it as:

 

"If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer. ... "

Around here we refer to it as "the 5-pound Ford carburetor adjusting tool."

[Wildman]

Yes, with the engine off, and after you totally bleed the system, you need to apply approximately 250 pounds of pressure to the brake pedal to re-set the differential valve.

[FxRacing282]

Of course, that simply follows the time-honored principle:

 

Nolite id cogere, cape malleum majorem

 

I know there's a formal translation, but I always like to think of it as:

 

"If In Doubt...Hit It With a Hammer, If Still In Doubt... Find a Bigger Hammer. ... "

Around here we refer to it as "the 5-pound Ford carburetor adjusting tool."

 

thats a good one.

[crlang2]

Well. I guess I have been overly cautious...

 

I'll try stomping the brake and see what happens. I may have to put the seat back in, sitting on the floor of the cab, I'm not sure I can apply 250lbs of pressure!

 

Thanks for the advice!