How to bleed rabs ? 94 4.0 ranger

[Rangerdanger411]

Soo my brakes are all screwed up. I got under my truck up to see if I had a brake leak because my fluid got low out of no where and my brake pedal would go slowly to the floor. I also notice the brake fluid was so dirty So being me I bled all 4 brake lines and a few days later I found the leak it was at the RABS. After that I jacked up my truck and remover both front tires and the driver side brake pads are worn out, passenger side is still in good shape same thing for the rotors So I was thinking I might as well change my whole brake system. Master cylinder , front pads & rotor & calipers and rabs. ( got new shoes, springs, hardware and drums for both rear brakes about 4 months ago)
I bench bled the brake master cylinder I did the method with the 2 hoses going out the master cylinder and into the revisor and pumping the cylinder till no air bubbles come out. Got that out the way and installed. Next I installed the rear abs but how in the world do I bleed it. Auto zone guy told me that opening that nut and normal brake bleeding should be the way. I did that with my partner for about and hour and got no fluid out. What is the way to bleed this thing ?

 

[Josh B]

Which nut is he talking about?

 

[Josh B]

Does the 94 have the same setup as the 93? Discs on front and shoes on rear?

 

[Rangerdanger411]

Yes that’s right

 

[Josh B]

I actually redid my whole system in 2006 or so, but I don't think it ever really came to be anything like it was supposed to be.
I learned that valve inside the rail wasn't working, as so many others had done, I wound up using mine as it was, basically no rear brakes.

I used it that way unknowingly through 4 600 mile(each way) trips pulling a loaded truck and trailer, and then using is ever since.

What I have learned about the valve is it is now policy to remove it, and run an open line to the rear

I am still using it 18 years on as is (with actually no rear brakes)

 

[RonD]

NO, the big nut is not for bleeding, fluid should never be inside that nut its sealed by a piston inside, so tighten it back up

ABS, anti-lock braking system
So braking should be NORMAL unless a wheel locks up, this means fluid pressure should flow from Master to each wheel normally until ABS detects a lockup, only then will a valve close to lower the braking pressure at that one wheel, in this case to BOTH rear wheels
(4 Wheel ABS units are different in that their internal passages can TRAP AIR inside, not so for the rear ABS units)

So Fluid should just flow thru that ABS unit if valve is not stuck, can/will take a few pumps but fluid will flow out, have to put your finger over the OUT line hole, like closing a bleeder, when helpers foot releases the pedal, so it doesn't suck back in the fluid

If front is done and sealed then if pedal keeps going down to the floor fluid is flowing down in the rear brake line, if valve is stuck then pedal won't go down to the floor, air in the line just compresses, so loosen the front IN line to let the air out and may be you can free up the stuck valve, unlikely but free to try

ABS rebuild seen here: https://www.ranger-forums.com/general-ford-ranger-discussion-15/rabs-rear-abs-disassembly-ranger-98-a-170733/

But shouldn't need to do that unless valve is stuck

More than a few bypass the ABS unit and install an adjustable proportioning valve
The Rear ABS never worked well especially if bed was empty, one wheel will always lock up because BOTH rear wheels are not monitored, only the differential is, ABS sensor is on the differential, so one axle/wheel can lock up without ABS detecting the lock up

Adjustable proportioning valve allows you to set the amount of braking you want from rear axle
Go to a gravel road and do some braking at speed, adjust rears so they don't lock up unless you want them to