help me diagnose my brake problem

[Brewmover]

I just replaced a large majority of my braking system on my 1977, but the brakes are soft to nonexistent. Can you all help me decide where to start my trouble shooting efforts? Here is what is new:
1. rear drums and all associated hardware
2. wheel cylinders
3. Brake lines steel and rubber
4. New front disc rotors and pads
5. Master cylinder (replaced this when I bought the vehicle and it worked prior to my efforts. I did not adjust anything here so I do not think this is the culprit)

Here is what is original (old):
1.Power booster (this worked before and I did not touch it so I doubt it is bad)
2. Proportioning Valve
3. I rebuilt the calipers per the tech articles listed on this site.

Once I installed all the new parts. I bled the brake lines starting at the rear passenger wheel, then rear driver, then front passenger and finally the front driver side wheel. I saw no air bubbles so I thought the system was bled properly. I did not pull out the brass nipple on the proportioning valve when I bleed the front wheels as I was told by a very experienced and seasoned bronco enthusiast that it was not necessary. The pedal went from soft to firm so I thought job done, right? After I applied the brakes for the first time with the vehicle in motion the brakes went soft.

I am thinking that I must have a leak somewhere and air is getting in, but I cannot find it. So where should I start? One thing that does not seem quite right is that the caliper is not real tight on the bracket that holds it. The key and "spring" thing just pushed right back in by hand. Should I replace the caliper key spring, or is this normal? The Calipers are on correctly (ie. bleeder screw up).

 

[surfer-b]

One thing that does not seem quite right is that the caliper is not real tight on the bracket that holds it. The key and "spring" thing just pushed right back in by hand. Should I replace the caliper key spring, or is this normal? The Calipers are on correctly

I doubt the spring is the issue, it may have some slop in it but will not cause the soft pedal. If you have checked and made sure there are no leaks I would replace the calipers, it sounds if though they are not sealing after the rebuild

 

[rmk57]

Is the brake warning light on your dash on? The brake proportioning valve may have to be reset or centered after all the bleeding you've done.

 

[bronco loco]

Make sure the calipers are set on the right orientation. The bleeder should be at the highest point. Went thru this situation not long ago. Post a picture of your calipers mounted.

 

[Brewmover]

Is the brake warning light on your dash on? The brake proportioning valve may have to be reset or centered after all the bleeding you've done.

What do you mean by recentered? The warning light is not on.

 

[rmk57]

What do you mean by recentered? The warning light is not on.

If your warning light is not on and the wiring is operating the way it should then its not the problem. Here's a step by step procedure for resetting them.



https://www.google.ca/url?sa=t&rct=...sW63-29KmbEpbppDg&sig2=H0_7yJkOE3fkGzm2GKiA5Q

 

[Brewmover]

Driver side caliper

 

[tirewater]

Did you adjust the drum brake shoes after installing the drums? My pedal was 'mushier' than I liked when the shoes were retracted too far inward.

 

[Apogee]

I would bench bleed the master cylinder used the plugged-port method. Then I would connect the rear brake circuit, leaving the front outlet port plugged and bleed the rear brakes until I had a good pedal feel and height. As noted above, there are procedures for adjusting the shoes so that they engage as they should without excessive drag or pedal travel. Next I would then connect the front brake circuit and finish bleeding the system. Doing it in this manner should help you isolate where the issue is, if there is one, by limiting the number of variables at any given time.

 

[bronconut73]

On more than one occasion we have seen folks ruin an old mc during the aggressive bleeding process.

Often times the bore in that old mc is nasty/rusty just beyond its normal pedal travel. When you start long stroking it during bleeding you pick up the nasty and rusty on the walls of the bore.

Check your mc thoroughly.

 

[Brewmover]

On more than one occasion we have seen folks ruin an old mc during the aggressive bleeding process.

Often times the bore in that old mc is nasty/rusty just beyond its normal pedal travel. When you start long stroking it during bleeding you pick up the nasty and rusty on the walls of the bore.

Check your mc thoroughly.

My MC is in great shape. It is less than a year old and when I open it looks new. No rust at all. I am about to dive back into this tonight. I intend to start with the rear drum adjustment as per the instructions in my Haynes manual. I adjusted them when I installed them, but perhaps I did it improperly. Any advice on doing this? Thank you all for the feed back. I hope the fix jumps out at me since I have had some time to stew on it.

 

[bronconut73]

My MC is in great shape. It is less than a year old and when I open it looks new. No rust at all. I am about to dive back into this tonight. I intend to start with the rear drum adjustment as per the instructions in my Haynes manual. I adjusted them when I installed them, but perhaps I did it improperly. Any advice on doing this? Thank you all for the feed back. I hope the fix jumps out at me since I have had some time to stew on it.

Well....
There is a little window on the back of the backing plate ...it has a rubber plug in it.
Pop the plug out and with either a brake spoon or an appropriately sized screw driver spin the star wheel on the adjuster.
One way will loosen the brake shoes the other way will tighten them.

You want a little drag when you turn the drum....not a lot of drag but a little.
Your self adjusters can do the rest.
To get your self adjusters to work a little quicker, get on an incline and drive up it then back down and kind of slam on the brakes....enough to make the car rock back a bit. That will click the adjuster once so depending on how close you got it manually it may only take a couple tries on the hill/incline.


By the way,

We have fellers on here at CB destroy a "brand new" master cylinder from the long stroke effort sometimes required to get all off the air out of our brake systems.
Even brand new mc's can have some rust on the bore where the plunger isn't sitting. And some new mc's have been sitting on the parts shelf for years too.

Just don't want you to forget to check on that mc again Bud.

 

[Brewmover]

Well....


By the way,

We have fellers on here at CB destroy a "brand new" master cylinder from the long stroke effort sometimes required to get all off the air out of our brake systems.
Even brand new mc's can have some rust on the bore where the plunger isn't sitting. And some new mc's have been sitting on the parts shelf for years too.

Just don't want you to forget to check on that mc again Bud.

Thanks. I will give it a closer look!

 

[Brewmover]

Ok I just jacked up the bronco and put it into neutral so that the rear wheels would spin freely. They move with some drag. So I think the rear drums are adjusted to the point that they contact the drum. If anything they might drag a little to much...dont know how to tell.
When I parked it I had pressed the brakes many times; could they still be engaged? Should I do anything to ensure that they are in their normal driving state (ie. no brake applied) before making an adjustment?

 

[Brewmover]

Thank you all for the help. All four brakes are working now. Needed a new driver side front disc caliper. Bled the brakes again and now it stops on a dime. The only problem I have now is that the driver side rear drum is too tight. It is creating a Doppler effect because it is not fully disengaging the drum. I tried to lift the release next to the adjusting sprocket but it would not disengage. Is there a trick to making it loosen up? Do I disengaged the sprocket and then use a screw driver to loosen it? I thought if I disengaged it it would loosen on its own...

 

[Slowleak]

Those adjusters can stick sometimes. You may need to hit it with some WD40 or brake cleaner.

 

[rmk57]

The star adjuster is only meant to go one way, to expand .
What you can do is use one screwdriver to push against the adjuster plate the star wheel rides against and another screwdriver to turn the star wheel to back off your adjustment. Not that hard to do.

 

[Brewmover]

The star adjuster is only meant to go one way, to expand .
What you can do is use one screwdriver to push against the adjuster plate the star wheel rides against and another screwdriver to turn the star wheel to back off your adjustment. Not that hard to do.

Tried that with no success. However, I was a bit timid with it because I thought I might bend something out to position or brake the star wheel. I will give it another try tomorrow.

 

[tirewater]

Is the e-brake cable stuck?

Spring pressure should retract the brake shoes when using the adjusting sprocket on the drum. You may want to pull the drum off (if possible) to check the assembly.

 

[Teal68]

Tried that with no success. However, I was a bit timid with it because I thought I might bend something out to position or brake the star wheel. I will give it another try tomorrow.

Just ot be clear....You don't have to bend or pry up the adjuster. Just push it away from the star wheel towards the outside of the vehicle. It moves away very easily so it takes almost no effort.