Chevy disc brake conversion with brake warning light

[hyghlndr]

This is my kit, I'm by myself, I'm sure I'm missing something, I wished it was like when I was young, I just bolded over everything but parts stores and businesses were a lot closer, I've watched many videos and they all look pretty much the same as far as assemble, where I live there's not much summer so might have to wait till next year!! Don't see much improvement! If you were down the street I'd hire you

Wish you were closer, would be glad to help. Kit looks good. Master cylinder or air in lines? I once found a ballooned hose...

 

[DirtDonk]

When these were still brand new and unmodified, you just drove them, played with them, worked with them and lived with them.
Now that they are more than 50 years old and heavily modified in some cases, it’s work, work work, and nothing but problems!
Normally, I wouldn’t wish on you that you were closer to this type of civilization. In this case it would be handy, but the overall trade-off probably isn’t worth it.
So be happy, close the barn door and maybe it’ll fix itself while you’re off hunting!

Or if we were all younger too, I bet a bunch of us would love to make a summer road trip and work for peanuts.
Well , more like burgers, dogs, steaks (along with the the occasional peanut of course) and brew.
Or in my case, ice tea, juice, or water!

In the meantime, good luck. Maybe we will still be able to figure it out from afar.

 

[DirtDonk]

Do you have another thread on this? We shouldn’t hijack gas pigs discussion too far. Maybe in your own thread we can discuss exactly what you’ve got, and what you had before.
Master cylinder is an important part of this equation as are several other things. And maybe if James Roney sees this, he can put to bed the discussion about whether or not fluid flow is actually impeded when the shuttle is offset to one side or the other.
The diagrams make it look like there is only a slight blockage when it moves to one extreme or the other. It would be nice to know if it does, in fact, effect braking if it is tripped.

Let’s get some more in depth going elsewhere and maybe you can still have some quality seat time before winter sets in.

 

[Gas Pig]

Ok update time. Well this build has been kicking and fighting me all the way. It’s going to be a great truck if I keep my sanity. All the trucks I have built to sell or for customers and the one that I just want to build a budget builder and keep for our family to use a drive it’s the problem project. At some point I’ll share all the issues I been fighting through.

Anyhow back to the brakes. So I tried to reset the shuttle every which way… opening the back brakes and having my son hit the pedal, tried the same with the fronts too. I also tried vacuum bleeding the backs while the front left caliper was left open, tried hitting the brake hard and kept pressure on the pedal for like 5 minutes. The best I could do is to get the light to off and back on with the release of the brake pedal. After all of that the brakes still not good.

So I bought a new proportional valve and the BLEEDING TOOL! So today I swapped out the proportional valve. While having the bleeding tool in I throughly vacuum bled the brakes! So I took it for a quick test drive (I left the bleeding tool in as well) my brakes were only slightly better but they still suck compared to other broncos I have driven. So I checked my booster… it holds vacuum the check valve seems to be working fine. I even put vacuum tester on my line (all rubber) going to the booster and at idle it was 12-13 and with some throttle it was up to 30. I think those numbers are good. Right?

So what am I missing? I first benched bled the master cylinder maybe not didn’t get all the air out? Maybe I just need to use the two person and bleed the brakes by pumping them up? Maybe my booster is still not working correctly ever though the booster would hold vacuum? What would cause it to have a fairly good pedal but not have good stopping power? Any thoughts?

 

[gnpenning]

Understand your frustration. I didn't go back through and reread the whole thread, just wondering what size tires are you running?

Do you have a soft pedal, does it bleed down with constant steady pressure?

What type of vacuum pump are you using to bleed with and are you sure you are getting a good seal with it??

Is it effectively pulling brake fluid through the system? Basically does it pull a good volume of fluid?

 

[DirtDonk]

I even put vacuum tester on my line (all rubber) going to the booster and at idle it was 12-13 and with some throttle it was up to 30. I think those numbers are good. Right?

No, it seems low.
How is this engine built? If it’s stock, your idle vacuum should be 18 to 22. If it is a heavily cammed, it could be much lower.
But 12 to 13 is very low for a vacuum brake unit.
And 30 is a strange reading to get with the throttle open. Was that under deceleration, or were you holding the throttle open. And if so, why did it change and get higher with the throttle open.
Where exactly are you getting the vacuum from?

What are your ignition timing settings?

 

[Gas Pig]

Understand your frustration. I didn't go back through and reread the whole thread, just wondering what size tires are you running?

Do you have a soft pedal, does it bleed down with constant steady pressure?

What type of vacuum pump are you using to bleed with and are you sure you are getting a good seal with it??

Is it effectively pulling brake fluid through the system? Basically does it pull a good volume of fluid?

Later today I’ll have my son help me pump bleed the brakes just to be sure. The pedal moves through the first part of the pedal but gets firm and doesn’t fade.

My buddy’s vacuum bleeder (four uncles from off of Amazon) which is newer and he had pretty good success bleeding his bronco brakes with it. It very well might be me… as the old adage say it not what you use, it’s how you use it! I did take my time and pull more then a pint of new brake fluid though the system. I started with the back passage rear then moved to driver rear and then passenger front and then to driver front. Each time closing the bleeder before shutting off the vacuum. I probably did each wheel 3-4 times and refilling the master after each bleed.

Right now I’m running 235’s as just rollers for test driving but I’m might run 30” or 31” so nothing crazy.

 

[Gas Pig]

No, it seems low.
How is this engine built? If it’s stock, your idle vacuum should be 18 to 22. If it is a heavily cammed, it could be much lower.
But 12 to 13 is very low for a vacuum brake unit.
And 30 is a strange reading to get with the throttle open. Was that under deceleration, or were you holding the throttle open. And if so, why did it change and get higher with the throttle open.
Where exactly are you getting the vacuum from?

What are your ignition timing settings?

So here is the start on opening up the can of worms! As you have been following my troubles with this truck…bought new & used, scavenge, and saved parts for this build for years! All in the interest of making a budget builder that the family could enjoy without killing the bank and or worrying the kids cruising around in very expensive build… just a fun safe driver. That’s my disclaimer!

As for my engine it’s not stock and it’s been gone through by someone and what was done with it I’m not 100% sure. What I can tell buddy bought a bronco 3 years ago and I heard the motor run and sounded great. He didn’t want it so I pulled it and sat on an engine stand for three years. There were my problems my have started? But for time’s sake the motor does sound like it has a cam but does have a bit of a rough idle too. It could be a vacuum leak if 12-13 and bouncing is low. Secondly it has a Weiand intake and a Holley 4 bbl. It’s also stock Duraspark with aftermarket coil but new Motorcraft ignition module and voltage regulator.

There is a couple vacuum ports on the intake one is going to the carb while a larger one is for the brake booster.

Things I should double check for?

 

[DirtDonk]

You might try setting the idle a bit higher.
Stock cam can easily idle between 400 and 600 RPM with no problem. A performance cam might need a minimum of 800, or actually prefer 1000 RPM idle. It just depends.
Not knowing means you have to experiment. And experiment, and experiment, and experiment…
It can be fun if you let it, or it can be drudge work if you’ve got more important things to do.

While you’ve got it idling at any speed, absolutely check for vacuum leaks.
Spray anything you want all around the engine, where air might leak into it the intake. This can be a spray bottle full of water, a spray can of WD-40, or a carburetor or brake cleaner.
I always liked carburetor cleaner, but the problems arise if you have fairly fresh paint on the engine. You definitely don’t want to let carb cleaner sit for more than a few moments on nice paint.
Brake cleaner evaporates more quickly, and usually doesn’t damage paint, but if you spray it often enough eventually it will. Hence the recommendation for WD-40 or water.
As you’re spraying, you’re looking for a change in idle speed and quality. You don’t care whether it goes up, or down. Only that it changes.
If you spray anywhere, and the idle changes, you have found a vacuum leak.

 

[hyghlndr]

At this point I would be considering a new master cylinder. So many new parts are junk.

 

[Gas Pig]

Update! Man this build is fighting all the way! So, getting the brakes a bit by bit… so I tried swapping the proportional valve like I said. The warning light is off but I still don’t have good brakes. Firm pedal but no stopping power. My next thought swap the vacuum booster. It seem to test fine but when I really put a leg into at a stop the engine starts to want to stall. I’m thinking my newer booster is actually loosing vacuum. Sure enough I swap it out for a used one we had kicking around and wow night and day difference. I actually have brakes, not perfect kind of a low pedal but the engine doesn’t want to stall.

But here is the kicker… now my second new proportional valve is leaking brake fluid from the brake warning switch. What the heck… I can’t catch a brake no pun intended! Is there an easy fix, like a new o-ring or Teflon tape the stupid plastic switch or does it have to come out a second time?

If you guys only knew about all the other crap I’ve been dealing with this build!