Brake Power Booster: Bendix Hydrovac

[Esteban]

The Bendix Hydrovac Brake Booster is another type of booster that can be easily installed in any car, since its location is remote. It is actuated by hydraulic pressure coming from the car master cylinder, instead of a mechanical linkage. The booster comes with its own master cylinder, where fluid is shared with all the system. It's not common any longer, but for sure can be found at wreckers everywhere. There's good information on how to rebuild them. A number of links are included. The beauty is how easy it is to install it since they just need to be spliced into the brake system in between the master and the wheel cylinders, they can be tucked away almost anyplace.

I used to have one like this installed in my faithful Patrol, until probably 12 years ago, when my other Patrol was totaled and part of the donor items included the booster that I have at the moment. It was located at the firewall in the same place as the heater, since I didn't have one. I used it for over 25 years without a glitch. Furthermore, there's no need to change the master cylinder.

This is a picture of the old Bendix Hydrovac that I have installed.

Bendix Hydrovac.jpg

Installation is very easy. A new brake line going from the master cylinder to the booster; a brake line from the booster to where the original brake line was attached; vacuum hose, and with that a good location to support the Bendix Hydrovac.

This is a nice picture of an application. Everything neatly in place. Check out the location:

Hydrovac example.jpg

Some useful links that I have collected over the years:

Bendix Hydrovac Overhaul
http://www.stovebolt.com/techtips/bendix/erickson/

Bendix Hydrovac Brake Systems (has good explanation about it's operation)
http://dave78chieftain.zxq.net/HydroVac_brakes.html

Another one from where I borrowed the picture:
http://www.jalopyjournal.com/forum/show ... p?t=771971

[bosque]

Within the second link from Esteban there was a link for an old film clip from the army explaining the hydrovac booster, very classic.

[moore_rb]

more very cool information...

[Swerve]

Great stuff Esteban

[bosque]

This is sinking in now.... in Estebans post I did not get that the hydrovac connects to a vac source, in our case I believe #5 in the manifold diagram....thats what that bolt/plug is plugging up.

[Swerve]

Could you just use a later style manifold which has vacum lines for the newer boosted brakes, or does it need a vacum pump on the belt drive?

[Esteban]

I think all Patrols came with that plug, so vacuum for a brake booster is there. There's where I have mine connected.

Do later models made for the Australian market have this plug?

[ckhorne]

I'm toying with the idea of adding a Hydrovac to my Patrol this spring...

I see that a number of them are available out there: https://www.google.com/webhp?sourceid=c ... c&tbm=shop

Given that this is a retrofit, does it really matter which one I purchase, or do they all work about the same, but with different brackets? Anything else I should look for?

[Esteban]

I'm toying with the idea of adding a Hydrovac to my Patrol this spring...

I see that a number of them are available out there: https://www.google.com/webhp?sourceid=c ... c&tbm=shop

Given that this is a retrofit, does it really matter which one I purchase, or do they all work about the same, but with different brackets? Anything else I should look for?

With the size of those Hydrovacs and the trucks that they are intended for, you'll have to probably put an egg between your foot and the pedal...

I don't know how sensitive your brakes will end up being. It will be good to know what size bore is the piston to have an idea. The only limitation that I can see of using this type of Hydrovacs, is that at the end you'll have a single circuit for your brakes like you have right know. Your master cylinder pump will remain.

[ckhorne]

With the size of those Hydrovacs and the trucks that they are intended for, you'll have to probably put an egg between your foot and the pedal...

That's what I'm having a hard time figuring out - I don't see any specs anywhere, and don't know if they're all generally the same or not. I suppose I could start cross referencing the vehicle they're intended for to see what works best for the Patrol.

Were you referring to just the first one listed? that one is for a 1952 GMC dump truck and probably would be a little overkill.

Something like this is intended for a '68 Chevy pickup, so may be better suited.

Thoughts?