Brake Help - Duff’s Monster Disc Kit

[mpboxer]

But the travel is still what is questionable. Any chance you can shoot a video, or maybe even take some steel photos with a ruler or tape measure in place so we can see how far the pedal goes?

First picture is normal pedal height NOT depressed engine OFF ~6 1/4”

Second picture is depressed pedal engine OFF ~4 1/2”

Third picture is fully depressed with engine ON ~3”

 

[mpboxer]

If the MC was bad it wouldn’t hold pressure right? When I do a hold on the pedal it does not move to the floor. No hydraulic leak.

I know the booster works as pedal drops after engine starts and it’s much easier to press brakes. I also checked for vacuum leaks.

I also verified booster to MC rod length again. It’s pretty much adjusted all the way out. Just enough to not contact piston in MC.

I confirmed rear drums adjusted to barely rubbing on shoes.

Verified prop valve piston is centered with warning light test.

 

[Jaybr]

I've got a similar problem with my hydroboost setup, pedal travels probably 3" and almost to the floor before it gets hard with or without engine running. It stops great but the pedal goes almost to the floor. I also have disc front and drums rear with an aftermarket proportioning valve from Duff's. Could never get the pedal hard with rear disc so pulled them off and went back to drums.

I'll be following this and try out whatever solution you come up with.

 

[mpboxer]

I've got a similar problem with my hydroboost setup, pedal travels probably 3" and almost to the floor before it gets hard with or without engine running. It stops great but the pedal goes almost to the floor. I also have disc front and drums rear with an aftermarket proportioning valve from Duff's. Could never get the pedal hard with rear disc so pulled them off and went back to drums.

I'll be following this and try out whatever solution you come up with.

Do you have the same MC (GM style equal reservoirs) as me? This make me think it’s either our MCs or prop valve. I was going to swap out the booster and bracket with my old one, but now I’m not so sure that will do anything.

 

[EPB72]

Do you have the same MC (GM style equal reservoirs) as me? This make me think it’s either our MCs or prop valve. I was going to swap out the booster and bracket with my old one, but now I’m not so sure that will do anything.

You can get plugs for the master cylinder outlets remove lines install plugs..pedal should little movement ..may point you in a direction...

 

[mpboxer]

You can get plugs for the master cylinder outlets remove lines install plugs..pedal should little movement ..may point you in a direction...

Duff’s sent plugs. May have to try this again. I did that while bench bleeding to confirm it does hydrolock. I think it was a recommendation on a different thread by Apogee. Perhaps if I do one reservoir at a time it will at least isolate the problem to front or back.

 

[Jaybr]

My MC is same style with one side plugged. I also tested it on the bench with all ports plugged and it locks down hard.

 

[toddz69]

And you swapped the lines so front reservoir goes to front brakes and rear reservoir goes to rear brakes, correct?

Todd Z.

 

[mpboxer]

It was the booster and bracket. I swapped my Toms (two years old) one back on and the brakes are great. Instant pressure when pedal pressed. There is more travel but I think that is inherent with discs. I’m attaching a couple pictures showing what I think the issue is. Duff’s supplied a heim joint which I think they did to try and alleviate the even worse angle with the clevis. Both options have the input rod at a bad angle. The heim also allows for “slop” in the linkage. Easier to see in a video.

Additionally there weren’t enough threads on the booster to MC rod for adjustment. The threaded head was out all the way held in by a couple turns. That may have caused flex too. It should be about an 1/8” longer.

 

[toddz69]

Are you using the Tom's kit with the 9" booster? Agreed on the photo that shows binding - that's not good.

Todd Z.

 

[mpboxer]

Are you using the Tom's kit with the 9" booster? Agreed on the photo that shows binding - that's not good.

Todd Z.

I'm using their 8" 76-77 booster:

https://tomsoffroad.com/parts/76-77-ford-bronco-power-brake-vacuum-booster

And their bracket:

https://tomsoffroad.com/parts/66-77-ford-bronco-power-brake-booster-bracket

 

[mpboxer]

I just want to update this thread and let anyone reading know Duff's has reached out to me and we are working on solutions. Thank you to all our great Vendors. We appreciate you!

 

[Jaybr]

Glad you got it sorted!

That's not the fix for mine, almost certain mine is downstream of the pedal/MC. Bronco was in storage for a year, and trying to remember what all I tried and I did plug the MC on the truck and it correct problem.

 

[DirtDonk]

If you have rubber lines going from the frame to the axles, there are ways you can gently crimp the hoses one at a time to see if the problem goes away. They have tools for that, but you could probably rig something up with some extra padding and some vice grips.
I don’t think you wanna try that if you have stainless braided lines.

If it does go away then you move on down to the next set of lines in the front (again, unless they’re stainless) and try again.
You can disconnect the lines from the proportioning valve and use caps to plug the lines ports. But that means another bleeding process, so not the most fun way to test. But sometimes necessary.
Would not be the first time that an aftermarket prop valve caused unusual symptoms.

mpboxer made great use of his phone camera during this process. Could see exactly what was going on with each component.

 

[mpboxer]

Glad you got it sorted!

That's not the fix for mine, almost certain mine is downstream of the pedal/MC. Bronco was in storage for a year, and trying to remember what all I tried and I did plug the MC on the truck and it correct problem.

Some once told me. Stay Motivated!

 

[Jaybr]

I've moved and have a new garage and Bronco's are now back with me, I'm motivated. Waiting on a lift to arrive and be installed on 2/28 then I'll get back on it. Planning to pull the body so I'll work on brakes again when putting it back together. All flex lines are stainless, hardlines Nicopp.