Topic: brake light

[95yjman]

Every since I did my D44 swap my brake light on the dash has came on. I converted the 44 to disc brakes, I did cut the parking brake cables. I've tried lifting up on the parking brake pedal to see if that turns it off and doesn't. The master cylinder is full of fluid, I've bled the brakes over and over again, and even did it with the motor running. Still on, I even bled the little due dad under the master cylinder. Any ideas? I dont' really want to just pull a fuse or something because I want it to come on if I have a problem or something.

[oldjeep]

There is a piston in the prop valve which slides to the front or rear when there is pressure loss - like a brake leak.

The piston is either stuck or you still have some air.  If there is no air in the system you can usually force the piston to reset by pressing really really hard on the brake pedal.

[95yjman]

hmm, I don't know, I pretty much tried standing on it, didn't go off.  i don't think I have air in the lines. kinda a dumb questions but do you have to press really hard and hold for a bit to try and get it to reset?

[dwtaylorpdx]

The piston slides to block flow to reduce fluid loss.

AS I recall sometimes you have to remove the cap and push the end of the piston back manually before bleeding.

Dave

[sharpxmen]

this is from FSM - it explains how it works but not how to reset it

Combination Valve
A combination valve is used in all models. The
valve contains a pressure differential valve and
switch and a rear brake proportioning valve. The
valve is not repairable. It must be replaced if diagnosis
indicates this is necessary.
The pressure differential switch is connected to the
brake warning light. The switch is actuated by movement
of the switch valve. The switch monitors fluid
pressure in the separate front/rear brake hydraulic circuits.
A decrease or loss of fluid pressure in either hydraulic
circuit will cause the switch valve to shuttle to the low
pressure side. Movement of the valve pushes the switch
plunger upward. This action closes the switch internal
contacts completing the electrical circuit to the red
warning light. The switch valve will remain in an actuated
position until repairs are made.
The rear proportioning valve is used to balance frontrear
brake action. The valve allows normal fluid flow
during moderate effort brake stops. The valve only controls
(meters) fluid flow during high effort brake stops.

[oldjeep]

hmm, I don't know, I pretty much tried standing on it, didn't go off.  i don't think I have air in the lines. kinda a dumb questions but do you have to press really hard and hold for a bit to try and get it to reset?

Yes, you have to stand on it pretty hard.  One of the things I like about using a pressure bleeder rather than pumping fluid with the pedal is that it resets the piston automatically.

[95yjman]

Well while messing with it, I think the old e brake peddle was causing it, I lifted up on the peddle it shut off heh 

Kind of a random question but, I'm running stock brake lines up front, if i where to get stainless steel braided lines up front would it stiffin my peddle feel? I'm runnin stainless steel in the back...

[sharpxmen]

i would say not too much (maybe a little) - sounds like you still have air or maybe your calipers are not centered and when you lift the pedal the pistons get pushed too much back.

[oldjeep]

The pedal feel is because you are running 4 wheel discs on a master cylinder meant for a disc/drum setup.  The only real fix is to use a master cylinder that is designed for a disc/disc setup.

[Torch_Ind]

The pedal feel is because you are running 4 wheel discs on a master cylinder meant for a disc/drum setup.  The only real fix is to use a master cylinder that is designed for a disc/disc setup.

that could be your prob with the light also

[95yjman]

The pedal feel is because you are running 4 wheel discs on a master cylinder meant for a disc/drum setup.  The only real fix is to use a master cylinder that is designed for a disc/disc setup.

Where could I get one? heh

[oldjeep]

Where could I get one? heh

There are many ways to go.  You could go with a grand cherokee MC and prop valve, or the popular corvette MC.  I use a 78 Merc Marquis master cylinder on the stock booster with my 8.8 rear disc setup.  Do some searching and you'll find writeups on many different swaps, with as many opinions on which works best.

I'm able to lock 35" tires without any problems on mine.