Hydro-Max Brake Assist *pics added* (long read)

[jesusgatos]

In the meantime, let's put together a short list of all the technical information that we might need to provide in order to get some definitive answers.

1) two axles vs. three axles

2) There are two different sized wheel cylinders for the A2 & A3. What are the piston sizes (diameter) for each?

3) What about the brake drums/shoes? Is it just the diameter and the swept area that we need to know? Maybe the total surface area of the brake shoes too?

Anything else?

 

[SuperJoe]

 

[jesusgatos]

Just talked to 'someone' who runs a high-performance brake company and has about 50yrs experience working with braking systems and components. He asked me not to use his name (again, due to liability), but was willing to take a few minutes out of his day to answer some of my questions about how to select hydro-max components for this application. Realize that this information might be a little more credible if I was able to cite the source, but was lucky to get any assistance at all. So anyway, here's what he told me:

The hydro-max master cylinder / booster setup in the medium-duty trucks is pretty much the same (unchanged) over the years, so the only thing we need to be concerned about is selecting a unit with an appropriately-sized master cylinder. And regarding the size of the master cylinder, he didn't care about the diameter of the wheel cylinders or the brake drums. Said that since we're sourcing parts from other applications, and there's not much to choose from, there's no point in getting into the details (he's a busy guy). The long and the short of it is that there are 1 3/4" and 2" bore master cylinders available, and he said that we'd definitely want to go with the 2" version. But he couldn't tell me off the top of his head what applications had that 2" master cylinder.

So that's what I'm on the hunt for now. A 2" master cylinder/booster unit. Would prefer to buy new/rebuilt, as I'm planning on adapting these parts to the stock pedal assembly, so don't need anything else, and would rather not use junkyard parts. If anybody can help me source parts, I'd sure appreciate it. Know a lot of different trucks used these brakes, and imagine that prices for replacement parts are going to be all over the place. Ready to buy parts over here...

Oh, and one last thing. He also confirmed that Jake0147 was 100% correct about pressure being equal at all three axles in a two-circuit system (front axle / rear axles), as long as the master cylinder doesn't have a step-bore. Jake's explanations were very clear and made perfect sense, but it never hurts to get a 2nd opinion.

Full steam ahead. Let's get this figured out!

 

[jesusgatos]

Almost forgot to mention that there are 12 and 24V booster units available. So we need to find a unit with a 2" bore master cylinder and a 24V booster.

 

[m-35tom]

jesse, isn't the small electric pump on the unit just for the times that the main hydraulic supply fails or cannot provide enough flow? so you are going to need a larger supply pump? why not just hydro-boost instead. simpler and smaller, and finding 24 volt pumps is going to be a lot harder. and just to confirm, there is no need for a proportioning valve, as all wheel cyls are the same size.
(having power steering would solve most of this!)
tom

 

[jesusgatos]

Hi Tom. Yes, the electric booster pumps are just for backup/emergency use. But it's a feature that I really like, and the hydro-max stuff is just a better fit for this type of application than the smaller hydro-boost components. I do/will have power steering, using the gear-driven pump on the new LDS engine that I'm installing, and that will also be powering the hydro-max brakes.

 

[spicergear]

One other time the electric booster comes on is if you get into your vehicle, put you foot on the brake and hit the key. The control circuit (factory stuff) would tell the motor to spool up because the engine isn't running and brakes are being asked for by the pedal being pushed. Basically when the key is ON and the engine is OFF... the booster will run when the brake is applied.

I'm still REAL happy with my HydroMAX set up on my 18,000lb deuce crane truck. As soon as the engine fires, *POOF* full brakes.

 

[jesusgatos]

So do you know what piston diameter you have spicergear? And is yours 24V?

 

[spicergear]

Yep, 50.8mm I believe is cast onto the side of the housing. ...yeah, so 2".

You may want to reread a few of my early posts. There are some HydroMAX details in there that may be helpful...especially the brake power multiplication vs hydro-boost. These are massive in comparison.

 

[jesusgatos]

Awesome, thanks. But don't remember reading anything about the 12 vs. 24V boosters. Is the unit that you've got 12 or 24V?

 

[jesusgatos]

Can anybody help me source these parts?

Spent this morning visiting Napa (can't get Bosch parts) and a few big truck places (can't find any 24V applications). Local International dealer quoted me $850+ for a master cylinder and brake booster, and I would still have to buy another 24V booster pump separately. So unfortunately, new parts might not be in the budget. But if I have to source parts from a salvage yard, would still be really helpful to have a better idea of how to find what I'm looking for. Just got off the phone with Bosch parts department, waiting for a call back, hoping to get some parts numbers for the following:

master cylinder with 2" (50.8mm bore)
24V booster assembly
24V booster motor (separately)
pedal rod ends (double clevis-type & threaded-type)

 

[jesusgatos]

Well Bosch was absolutely no help. They told me that they don't have any parts numbers (at least, not that they were willing to give me) and that all parts and support for Hydro-Max brake systems goes through the dealers for the manufacturer of whatever vehicle is/was equipped with that system.

 

[silverstate55]

Sounds like you need to make friends with someone who has access to some Hollander interchange manuals, and source a used or rebuilt unit from one.

 

[jesusgatos]

See, that's what I need to know. Don't even know what a Hollander interchange manual is!

 

[spicergear]

Awesome, thanks. But don't remember reading anything about the 12 vs. 24V boosters. Is the unit that you've got 12 or 24V?

I originally posted early in the thread that they were available in 12 or 24V. Mine is 12 volt.

 

[jesusgatos]

Yeah, I read that in one of your posts and in one of the PDF's posted, but am having a hard time finding a 24V booster assembly.

 

[spicergear]

You may want to check with an International parts desk. See if they can locate one since they were later model civvy (commercial) and military.

 

[silverstate55]

As for the Hollander's, you can find them at a decent heavy-truck salvage yard, or sometimes a very good auto parts store (NOT one of the national chains). One of our local NAPAs has a couple of great countermen who really know their stuff & how to find what you need. Most of the salvage yards have access to their computerized parts locator services to search for what salvage yard would have your parts, if they didn't... The key indicator for your needs is 24-volt, not 12-volt, of course.

HTH to get you started. Spicergear also has a great suggestion in starting with Navistar dealers, since a lot of Hydro-Max systems were used on S-Series medium duty trucks from the mid-70s through the 90s.

I'm looking at a complete Hydro-Max setup on a chassis from a 1994 Chevy C5500 sitting in my side yard, but it's 12-volts with a Metric steering box. It will stay with its original application, while I search for another to use on my Deuce. What I plan on doing is sourcing a 12-volt HM system, and use my second 12-volt alternator & dedicated battery to power it, separate from the 24-volt system.

 

[silverstate55]

Some online places to start your search:

Heavy Truck Parts Search: HeavyTruckParts.Net - Find Used, Salvage or Rebuilt; Engines, Transmissions, Rears, & More!
LKQ Valley Truck Parts & Equipment (Fresno): Valley Truck Parts
LKQ-ACME Truck Parts (Stockton): Truck Parts and Equipment - Used Diesel Truck Parts | Acme
Specialty Truck Parts Inc (San Jose): Specialty Truck Parts Inc.

These 3 CA vendors have helped me in the past when I corresponded with them, while searching for specific parts for non-military trucks. You might know of some closer to you, I'm just not quite sure where you are located. You can find a closer LKQ vendor to you by using HTP site.

HTH, good luck!

 

[jesusgatos]

You may want to check with an International parts desk. See if they can locate one since they were later model civvy (commercial) and military.

Spicergear also has a great suggestion in starting with Navistar dealers, since a lot of Hydro-Max systems were used on S-Series medium duty trucks from the mid-70s through the 90s.

Went to an International dealer yesterday and they weren't able to find any 24V applications/parts.

What I plan on doing is sourcing a 12-volt HM system, and use my second 12-volt alternator & dedicated battery to power it, separate from the 24-volt system.

That's an option for me too, as I'll have a separate 12V alternator and charging system onboard too. But would like to reserve that for the motorhome side of things, and run everything related to the truck on 24V. Might reconsider if parts are unavailable or ridiculously over-priced though.

As for the Hollander's, you can find them at a decent heavy-truck salvage yard, or sometimes a very good auto parts store (NOT one of the national chains). One of our local NAPAs has a couple of great countermen who really know their stuff & how to find what you need. Most of the salvage yards have access to their computerized parts locator services to search for what salvage yard would have your parts, if they didn't... The key indicator for your needs is 24-volt, not 12-volt, of course.

Some online places to start your search:

Heavy Truck Parts Search: HeavyTruckParts.Net - Find Used, Salvage or Rebuilt; Engines, Transmissions, Rears, & More!
LKQ Valley Truck Parts & Equipment (Fresno): Valley Truck Parts
LKQ-ACME Truck Parts (Stockton): Truck Parts and Equipment - Used Diesel Truck Parts | Acme
Specialty Truck Parts Inc (San Jose): Specialty Truck Parts Inc.

These 3 CA vendors have helped me in the past when I corresponded with them, while searching for specific parts for non-military trucks. You might know of some closer to you, I'm just not quite sure where you are located. You can find a closer LKQ vendor to you by using HTP site.

HTH, good luck!

Thanks!