Alright guys I'm in need of some big help. The master cylinder in my 1988 Bronco (302) has been going out for about 2 months. I was up to pumping the brakes 3 times before I got enough pedal to stop. I just finished changing the master cylinder. I bench bled it before installing it. I started the Bronco and pumped the pedal a few times. Ii now have fantastic brakes. The problem is that they work without pushing the pedal. They feel as though they are stuck. When I put it in gear the brakes wil actually keep the Bronco from moving. Also the "red" brake light (e brake?) and the rear antilock idiot lights are on. I am going to go bleed the lines and hope that helps but this didn't seem like that kind of problem... One other idea I had was did the rear brakes adjust way out because my master cylinder was going bad for so long. Any help will save the day... Thanks guys. (and gals).

 

Well I am now rotating the tires and have found that it is the rear brakes only that are locked up.

 

Did you bleed all the brakes after you changed the master cylinder, incuding the ABS module under the drivers foot well?

With the E-Brake light on it might suggest that the mechanism connected to the e-brake pedal isn't releaseing. Check that the wire running along the drivers side chassis rail is loose (i.e. when you grab it you can pull it away from the chassis) if its not then the e-brake is jammed on.

There is a way to pull the codes from the ABS unit but I don't remember how - someone on here will tell you quicker than I can run out to the truck and get the book no doubt.

 

Just re-read your post about the master cylinder actuator - if you've not reset the pushrod length according to the book you'll be applying constant pressure to the brakes which might also account for the problems you got.

 

I would guess that your abs valve is on its way out the door. I had the same exact thing happen to me on my 88. The e-brake light was on along with the orange dummy light. My back brakes would lock up and get hotter then heck. I replaced the valve and have had no problems since. There is electrical going into the valve and that is what causes your dash lights to turn on. Although, like muckypaws said, try bleeding it while the truck is running first. You should always have the truck running while you bleed that valve because of the electrical.

 

hmmm thats interesting... I bleed mine whilst the motor was off. didn't think about the electrical having an effect on the fluid... maybe i'll try it again some time.....

 

I read on the abs valve thing that it needed to be done that way because the abs does not work with the power off. I was also told by a buddy that is a Ford guru that it should be done while the engine is running also. I could be wrong, but I do it just because it makes me feel better.

 

As stupid as this sounds I somehow took care of my light problem. If I slide the sensor? under the master cylinder resevoir all the way in it turns on my anti lock light. Sliding it out just a little turns it off. This may be a bad sensor not sure. I have bled all the lines. My last problem is now when I mash the brakes to stop quickly, the right rear only locks up. I then have to either manually adjust iit out to release the brake OR open the bleeder valve. My thought was that maybe the pads and drum are so worn that it allows the brakes to travel to far out which puts the "valve" in the drum in a bind. It could also mean that because my master cylinder was going out that I possibly didn't have this problem before because that brake wasn't working. i.e. stopping the Bronco with only 3 of the brakes. I hope this makes sense.

 

Sounds like air in the ABS valve. If air got into it while changing the master cylinder, then you will need to bleed the valve. There is a very specific procedure for bleeding the valve, as far as which part is bled first and if that procedure is not followed then the valve will not work properly and damage can also be caused to it necessitating replacement.

I do not know the specific procedure but you could probably do a Google search to find it, if not let me know, I have a shop manual and can look it up.

The rear brakes being locked up after a master cylinder change is definitely a symptom of air in the ABS valve - and the lights back this up.

I got lucky when I changed my master cylinder. It did not seem to want to bench bleed properly - it would not pump up even though I repeated the bleed procedure about twenty times. I finally got fed up and stuck it on the truck, thinking that I could bleed it there with the pedal if I needed to. But the brakes worked perfectly from the get-go. I didn't have to bleed anything.

 

I have the same problem but mine lock up randomly. Would air cause this or could the valve just be bad.

Luke

 

when you bleed the brakes you always start at the right rear tire, then LR , RF, LF in that order.

 

I had goodguiys flush the entire brake system. I guess I am wondering if they didn't bleed the ABS valve right or it is just bad. What's a new one cost?

Luke

 

Since I started this thread I thought I should update everyone.... I finally gave up and have taken my Bronco to a mechanic friend. He is looking into my problem. He's slow but very good and super honest. I will let everyone know what the outcome was when I get the beast back. Also would like to thank everyone and every idea.

 

I have gotten word that my proportioning valve is shot. At $200 from ford to fix it is sitting. Any ideas to a cheaper solution would be great. Thanks.

 

have you called napa etc.. for that part.