Hi And Thanks in Advance:

I just did front brakes on my 93 Aerostar, 2 wheel drive. I usually pump the pedal with the engine off after doing the brakes, to get the pedal back, this time I did it with the car on. (It shouldn't matter???????). Everything is working properly, good firm pedal etc, however the ABS and Brake Lights are on. This never happened before. I tried to disconnect the battery to see if that would clear the problem it didn't.

I only test drove a few blocks, no problems. Please advise.

Thanks
Frank D

 

Check to see if your brake lights (in the tail light housings) are burned out. If they are, the condition can also disable your cruise control and prevent the transmission to lock its torque converter. If you have 4wd, that will be disabled as well. All that from burned out brake lights.

 

Thanks for the reply, the lights are working.

 

The other thing is while you were pumping the brakes back up, you pushed the shuttle valve in the master cylinder to one side. You can check this with an ohmmeter or a test light on the sensor switch on the MC. It is the switch on the front end of the MC body itself, not the one in the side of the plastic reservoir. There are two pins on it, but they are connected together, so you can put one probe of your ohmmeter on one of them and the other to a ground point. If the resistance drops to zero, the switch has been tripped, and it means you did push the shuttle valve toward the rear circuit of the MC. (You only worked on the front brakes, right?) You need to open up one of the rear bleeders and carefully pump the brake pedal hard enough to push the valve to the other direction to center it in the MC, but not so hard as to push it too far in the other direction. I used a DMM with a beeping continuity tester, and manipulated the valve until the DMM stopped beeping. At that point, my brake and ABS lights went out.

If you're using a light, you want to connect one end of the light to one of the pins on the switch and the other end to the positive battery terminal. If the light comes on, the shuttle valve has been pushed to one side, and you want to jock it so that the light turns off.

Another possibility is the switch may be internally shorted by fluid leaks. You can pull it out and clean off the corrosion that's causing the short.

 

Thanks xlt4wd90

I only worked on the front brakes. Initially the pedal was low and came up nice when I pumped it (as they usually do). I have over 115K on the Aerostar and have done many brake jobs, this however is a first.

Thanks for the help!

I will try the test light to see. I have a feeling you are 100% correct! I will have to bleed the rear brakes to center the valve in the MC. (How will I know when I have bled them enough? Will the lights go out? As you can tell I am a backyard mechanic, I have a nice set of tools however I don't have DMM with a beeping continuity tester.

Sorry for all the Questions!

I was hoping driving would resolve it .

Thanks
Frank D

 

Hi Frank,

I'm a backyard mechanic as well, like a lot folks here.

If you have a light to test continuity, and it does come on when you hook it up, you can just watch the light as you pump the pedal. You will have to pump about as hard as you did when you were bleeding the front brakes. You may actaully hear the valve go "click" as it moves. The idea is to use hydraulic pressure to push that shuttle valve back in place. The cause of the problem was most likely doing this with the engine running, so that you had a lot more power assist than you needed to pump the pistons back into place in the calipers.

When you do get it back in place, it will stop making contact between the switch and ground, your continuity checker light will go out, and the brake warning lights will go out. More importantly, both your brake circuits should start working properly again.

god luck,
eugene

 

Thanks Eugene,

I knew after I finished the one thing I did differently was pump the brakes w/ the engine running. No big deal I guess, but more work than I was looking for. You can bet I will never do it that way again.

Once again thank you!!!!!!!!!!!!!

Frank D

 

Hey Guys!
I'm planning on bleeding my brake system this weekend
(ABS light & spongy). I've done this on smaller vehicles but nothing with power brakes. I've read the manual and couldn't find if when bleeding the system, should the engine be on or off when pumping the pedal? Also can you bleed the MC on a 93
and if so how?
Thanks for your post and replys
Andrew

 

afcro,

From what has been posted above, bleeding the brakes with the engine running may give you too much power assist causing the proportioning valve to shift position and turn on your ABS and Brake lights. On bleeding the master cylinder, you might just loosen the lines a little, but you take the chance of getting air in the lines.

xlt4wd90

My 92 3.0L 2wd has a separate proportioning valve which is not a built-in part of the MC. It's located below the MC on a bracket attached to the MC mounting bolts. Below and to the rear of this proportioning valve is the ABS valve.

I have a similar problem with both lights on after repairing a broken front brake line, a rear leaking wheel cylinder and manually bleeding the brakes. Troubleshooting the system I determined that the proportioning valve is shorting to ground, so it has been tripped. Is it possible to tell whether it's tripped due to the front brakes or the rear brakes? Can the proportioning valve be dismantled safely without removing it from the system?

Any help would be appreciated.

Ron

 

Ron,

Your setup is a little different from mine. My 90 model only has the ABS valve mounted below the MC; I do not have a separate prop valve. I would have thought that the ABS valve would serve as a dynamically adjusted prop valve. Does it have two little cylinders sitting on top of it, and an electrical connector to the left side?

Unfortunately, I have no experience with the ABS system. All the references I've seen regarding servicing them involves some form of electronic test equipment from Ford. So my strategy has been to leave them alone, and hope I never let the reservoir run dry when I'm bleeding the system. I've never opened that valve before.

Even in a system with a separate prop valve, I would expect the shuttle valve to be in the MC, since that's where the dual brake fluid circuits are. Does your MC have an electrical switch and connector on its very front tip? That's where the shuttle valve sensor should be. If one end of the system is leaking fluid excessively, the shuttle valve will be pushed toward that side to cut off fluid flow. So I would expect if you did that, it would be stuck in the rear circuit, since that's the end you were bleeding. I would crack one of the front bleeders and pump the pedal. Again, you may have to hit it kind of hard to push the shuttle valve away from where it is now.

Sorry I can't be more help.

good luck,
eugene

 

eugene,

Thanks for your reply. I guess that FORD redesigned the system for 92 as mine includes the separate proportioning valve.

My MC does not have the shuttle valve on it. My ABS valve is the same as you describe. The prop valve is located between the MC and the ABS valve, both physically and hydraulically. The prop valve has two connections from the MC; one for rear, the other for the front brakes. The prop valve has three out feeds, one to rt front, one to left front, and the last to feed the ABS valve.

I remember seeing an article online by Bill Williams, Brake & Front End Magazine, about troubleshooting the Ford brake system that had detailed pictures of the various components, but I can't seem to find it again. I think it was from the June 1999 issue. I was just hoping someone may have had experience servicing this separate prop valve.

Thanks again.

Ron

 

Well the weather warmed up a little and I bled the left rear brake hoping to get the ABS and Brake lights to go off. No leaks, no air, nice pedal. ABS and Brake lights are still on. Any suggestions.

Thanks and Happy holidays
Frank D

 

Frank D,

In a related post, aerocolorado has a link to an article that explains the Ford brake system components and how to test them, try this http://www.babcox.com/editorial/bf/bf69936.htm


LOL

Ron

 

Thanks Ron,

I guess at this point I will try bleeding one back wheel cyl. again and tap on the master. I will do it with the engine off, disconnect the battery in case it stores a code 4, and see what happens. Worst case is the master needs replacement.

What a PIA this turned out to be.

Frank D

 

Frank D,

Don't feel bad...we've all had the same problem with this d--n system..seems like Ford could have designed it a little better or at least provided a way to bleed the brakes while isolating the switches for brake changes...Guess they wanted us to have to go to the dealers..

Have a Merry Xmas and Happy Holidays to you and yours

Ron