from https://www.ford-trucks.com/forums/5...-calipers.html

Thanks for the above detail. But how does one bleed the combination valve? Which connectors or plugs does one crack open?

Also how does one bleed the RABS valve? Which connectors or plugs does one crack open on that one?

I have just installed a new Master Cylinder and have already tried to bleed system without knowing the proper order as documented above. I just don't know how to properly bleed the two valves mentioned above.

My current symptoms are:
Brake Pedal is somewhat soft when not running. Pedal is hard when both outlets on the MC are plugged with plastic plugs that came with the new Cardone unit. Does that indicate that both chambers of the MC are good?

When running, brake and ABS light are off. Pedal is very soft. If pressed to the floor both lights come on.

The reason I replaced the MC is because the pedal got soft and the lights came on in heavy braking. Fluid was very dark, but is clear now. No leaks.

Thanks in advance for any help.

 

did you bench bleed the master?
howto:
1.keep plastic plugs in and hook up to booster and tighten
2. pour break fluid in till full
3. press in break lightly numerous times until all air is out of master
(you will see bubbles) you do NOT need to push break in far
4. hook up lines to master and bleed them.

 

I forgot, is the Aerostar's master cylinder one of Ford's fast-fill designs? There's a trick to bleeding those that involves lifting it (or the car) one way, press down, then lifting it the other way, then release.

 

Yes I did bleed bench bleed the MC.

The installation instructions for the 1995 master cylinder mentioned that some types of master cylinder should not have the plunger released quickly during bench bleeding because it could cause many bubbles in the fluid. It seems this is that type since it appears to have happened to me (lots of bubbles) since I did release it quickly because I figured it did not apply.

The instructions were not clear on whether or not to release the plunger quickly for the Aerostar. They said to wait 20 seconds I believe for each actuation of the plunger.

 

I re-did the bleeding, using the correct sequence and the pedal is better. I didn't open any of the lines going into the proportioning valve or the ABS valve.

 

I still get the brake and ABS lights on pressing the pedal very hard. If I disconnect the ABS controller under the ash tray, the lights don't come on when pressing hard on the pedal, even with the van running.

I now figure that the value is bad after pulling the codes from the ABS Controller. I got a code 4.

 

it's probably the combination/proportioning valve slide piston that is out of position. it's on the end with the large threaded cap with the rubber plug in the center.
do not remove the cap, under high spring pressure. parts fly
don't ask how I know.

been years since I had to take mine apart and clean it so that part of memory is gone. the slide valve collects water, corrosion and dirt, jams. it also operates an error code switch for the brakes

there are threads here on cleaning and disassembly.

 

Thanks for your reply.

The Error code 4 I got was from the ABS Control module, not the general computer.

I don't understand how the proportioning valve would allow the pedal to go to the floor.

I do understand that the ABS valve has a reservoir that takes fluid and that would allow the pedal to be pushed more.

Here is why I don't think it is the proportioning valve. It could be though since I don't understand it all well.

http://www.cardone.com/english/club/...%2012-0002.pdf

 

The master cylinder has that shuttle valve that cuts off the circuit that flows too fast, as in a leak. If you pushed the pedal too hard while bleeding one circuit (opened bleeder), it can push the shuttle valve to one side. If it's activated, it will trigger error conditions for every system that depends on the brakes to function properly, such as the RABS, cruise control, torque converter lockup, and E4WD, if you have that. The other thing that can happen is corrosion can develop around it and short out the sensor switch. Since you have a new MC, this should not be the case, but you can check anyway by unscrewing the switch on the front of the MC.

To re-center the shuttle valve, I usually use a DMM with a beeping continuity tester. Connect one probe to a ground, and connect the other to one of the pins on the sensor (switch). If it beeps immediately, that means the shuttle valve has activated. Crack open either a front or rear bleed screw, and hit the brake pedal abruptly, but don't go all the way to the floor. Sometimes you can hear the shuttle valve shuttle from one side to the other if you opened the correct bleed screw, and you push the pedal too hard. But assuming you opened the correct bleed screw and hit the pedal just right, the valve will move to its center, and your continuity tester will stop beeping.

 

I do have E4WD.

 

Never had a problem bleeding either of my 3 96's 0r the 94.. Biggest problem with brakes is the rear shoes out of adjustment or air in the system..Usually if the spool is off center a good slam of the brake pedal will center it if there is no leak.. Check for leaks on the side of the fuel tank..I never had to deal with bleeding abs and have had many blown brake lines in the past.


Dick

 

the later Aeros have a separate combination valve located in the brake line after and below the MC.

https://www.ford-trucks.com/forums/4...ion-valve.html

 

There are no leaks and I believe I have gotten all the air. I think the problem is the RABS valve is taking up some of the oil and therefore letting the pedal fall. Once I stop pressing on the brakes, the oil comes out of the valve again. I do have the 1995 as previously mentioned.

I wonder if I should get a new ABS valve or try a used one. It seems to me the used ones may all be wearing out after this many years.

 

Did you check the rear brakes? Rubber lines. When you pump the brakes what happens?



Dick

 

I examined every part of the system available. I replaced the Master Cylinder and since I broke off two bleeding screws I also replaced one caliper and one wheel cylinder. The system was thoroughly bleed after all this.

Nothing happens when I bump the brakes that is different from the initial application of the brake. It does not pump up, but still sinks almost to the floor when pressing hard on it with the motor on to boost the power brakes. The power booster seems to hold air because when I remove the hose there is a rush of air.

All test lights on dash work and shut off when starting the van. There is a single clicking noise (sounds like a reset) from the ABS hydraulic valve (I think) when the ABS light turns off after starting the van. On pressing the brake to the floor both the red brake light turns on and so does the ABS yellow light.

I think the ABS valve is not holding the pressure and or is releasing early (not leaking).

This all started after forcefully testing the brakes. Symptoms are the same as before I started working on it.