Braking options low vacuum . Possible manual brakes

[brocbronc]

My bronco is having serious braking difficulties due to the low vacuum the engine puts out. I don’t want to go hydroboost. Is there a manual braking option that others have had success with?

I have 1tons and 40s. Chev3/4 Tom brakes at all 4 corners.

Heard of the dodge d150 master
Also considering the Wilwood dual master setup with pedal assembly.

Any real world experience out there?

Thanks
Kevin

[CityHick]

Re: Braking options low vacuum . Possible manual brakes

The biggest problem is the tiny vacuum boosters that we can fit into our cramped engine bays.. barely adequate.

You could try running an electric vacuum pump like the hot rod guys run, but it's that tiny booster that drives so many of us to go hydro... Hydro is on my list.

But for reference: https://www.summitracing.com/parts/sum-760152

[70 Steed]

Re: Braking options low vacuum . Possible manual brakes

Why don’t you want to go hydroboost? It’s one of the best upgrades I’ve done.

[904Bronco]

Re: Braking options low vacuum . Possible manual brakes

It’s one of the best upgrades I’ve done.

Agreed!

[PhantomEB]

Re: Braking options low vacuum . Possible manual brakes

Yeah why not hydro boost? You and I got the same set up as far as brakes go... I need to look into what’s gonna provide enough piston capacity to feed big ass brakes.

[NorcalKD]

Re: Braking options low vacuum . Possible manual brakes

No issues here with vacuum boost brakes, very responsive after fine tuning.
Kevin- I can cruise by sometime with mine and we can look (5.0, d60,14b, disc, 41.5”s). After bleeding the brakes hundreds of times with constant spongy brakes I had to adjust the brake pedal some. I found I was not getting the full throw of the pedal to build pressure. Previously another time, I found my booster to have a hairline crack which prevented pressure building also.

[albino]

Re: Braking options low vacuum . Possible manual brakes

Like yourself, I didn't want any type of brake booster that relied on engine vacuum while wheeling.

I'm running a Willwood master cylinder only, and my braking is fine. I'm running D60's front and rear with discs on 40" Swampers. Not sure it will make a difference due to brake size, but when I had my axles built back in 2000 for my previous rig, I believe I had to use smaller discs from an El Camino so they would fit with a 15" rim (which was the standard wheel back then).

[DirtDonk]

Re: Braking options low vacuum . Possible manual brakes

What size master cylinder are you running albino? 1" maybe? How's the pedal feel now?

Paul

[California Monkey]

Re: Braking options low vacuum . Possible manual brakes

I'm running the heavy duty one from wild horses with no booster with tons and 40" tires. I can lock them up if I had to. I have drums in the rear

[albino]

Re: Braking options low vacuum . Possible manual brakes

What size master cylinder are you running albino? 1" maybe? How's the pedal feel now?

Paul

Off the top of my head, I don't remember. If I get some time when I get home I'll check.

As far as the pedal feel, it's 100% fine for me, on and off road. Is it super soft like a new car? No.
OTOH I've never felt like "man these brakes suck, and I need something better". Not once.

For wheeling, I've never wanted my brakes being assisted by something that relies on the motor running. My brakes feel and react the same when I'm motoring down the trail, as they do if I'm crawling down a rock pile, and the motor stalls.

[Efibroncoman]

Re: Braking options low vacuum . Possible manual brakes

You can go with a larger bore master cylinder if you can find one. I ran a 1-3/16” bore from a 90’s F-350 but it was tall so I cut a hole in the hood for it to stick out. I had planned to replace the hood and build a custom bubble over it but it didn’t happen before I sold the Bronco. Did make it possible to check brake fluid level while bombing down the freeway though.

[albino]

Re: Braking options low vacuum . Possible manual brakes

1" Bore size

https://www.wilwood.com/mastercylind...ter%20Cylinder

[DirtDonk]

Re: Braking options low vacuum . Possible manual brakes

Perfect, thanks. That's what size I'd hoped to see.
Surprised at the happy campers with larger master cylinder bores and manual brakes. Some are ok with them of course, but lots of people complain about the need to push so hard.
Maybe they're just used to more power from modern vehicles.

Paul

[brocbronc]

Re: Braking options low vacuum . Possible manual brakes

My brake feels firm when engine is off but soft and I have to pump to build pressure because the pedal hits the floor before building pressure. I may be going to hydraulic clutch which may interfere with the hydroboost bracket.

[DirtDonk]

Re: Braking options low vacuum . Possible manual brakes

The firmness when the engine is off means very little at this point. It's too hard to push through a brake booster unless there is boost. That's just how most of them work so your firm pedal is just the resistance from the booster.
The fact that it changes and you get some action when the engine is running means you actually do have enough vacuum to at least actuate it initially. The other stuff has nothing to do with lack of vacuum, other than maybe showing that something is physically wrong with the booster.

But at this point, the going to the floor, soft pedal, pumping to get the pedal to do anything all point to either air in the system or improperly adjusted mechanism.
Or a very imbalanced system.
I don't remember if you said, but did it just start doing this out of the blue? Or has it done it since you installed all the brakes?
And I don't see if you mentioned which master cylinder you have now. If so I missed it. You have big brakes at both ends possibly, so need more piston size in the master.
I say presumably because some 3/4t GM calipers are the same size or near enough to the same size as the 1/2t versions to make little difference. But if you have the big-big brakes that I think they had on some models, they may just need more fluid flow than your master is putting out.

But given the general history of bad adjustments on Bronco booster linkages over the years, that's sure where I'd start. Plus all the usual suspects...
Those would be:

1. Bleeders always up. Never pointed sideways or down if it can be avoided. Otherwise air won't bleed out.
2. Calipers not retracted, and pads in contact with the rotors.
3. Mounting brackets solid with no flex.
4. No rubber brake hoses at this level. Always use braided when max pressure is needed. Either way, no old hoses period.
5. Verify full flow at each corner when bleeding. And bleed, bleed, bleed and if you see air find out why before wasting your time bleeding any further.
6. Pedal rod length. Too short and you don't have enough travel if something happens.
7. Bad proportioning valve.
8. Bellcrank linkage solid and properly adjusted at the back of the booster.
9. **** Most Important Alert! **** Well, not necessarily the most important, but one of the most likely culprits on Broncos with custom brake systems. Verify that the booster rod is perfectly adjusted to the back of the master cylinder.
All of this attention to the linkage is very important because with a pedal ratio of approx. 6:1 every 1/4" of excess gap adds up to 1.5" of pedal travel. Add some air, some play elsewhere, and even with no other physical problems you have a brake pedal at the floor with poor performance.

If you've gone through all that, sorry for the repeat. But we're just starting from scratch here with your clues so bear with us as we try to diagnose the issue without seeing it.
And speaking of that, got any pics of this rig and it's brake details?
We like pics. And they do help sometimes too!

Paul