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

If you've not heard of this, don't feel bad. If, however, hydro-boost rings a bell then you're on the same page. Can't sleep so thought I'd post (will post pic some point today) about a project I've been working on. I pretty much expect some 'flaming' about this but I think I'm well prepared for it.

My air system on my truck has been a pain. From hissing lines to that infernal buzzer, to rusted air tank, and air pack woes...pushed me to looking for something...something better (flame on) or at least less headache.

I initially looked into the hydroboost set that has been used and adapted to about everything. Built an entire system, got it up and running but wasn't happy with the results. Found out a LOT of technical stuff about it and how to 'make' it work but in doing so would be pushing the design of that system to running at about 95% all the time. That's too much...especially when this ain't a racecar and it the brakes of a big dumb truck.

A gentleman named Paul at Hydratech mentioned the Hydro-Max system but said they didn't do much with it BUT, it was a substantially heavier duty unit and was designed for larger trucks. I took that and ran with it.

The hydroboost systems use hydraulic pressure from the power steering pump to assist the brakes in the same way a vacuum booster does. The system feeds the booster then feeds down to the PS box.

The hydroboost system has roughly a 7:1 multipication ratio and an 1-5/16" bore power piston that pushes the piston in the master cylinder. The Hydro-Max uses a much, much larger bore (must be 3" or more) and has around a 21:1 multiplication from what I've found. Hydro-Max is also rated up to 43,000# GVW and is found in all kinds of medium duty trucks from Ford 600, 700, 7000, etc to International S1700's and that monster pick-up looking thing...to name a few.

So anyway, I pulled ALL the air crap off my truck and started over. Like I said the first go was Hydroboost that didn't quite cut it. Second shot was the big hulking brother, Hydro-Max. I picked it up off of an Internation S1700. Master cylinder uses a 50.80mm bore (2"). I had already set up my CAT with a new PS pump from a '93 1 ton Chevy. I got looking around at the big truck lot and found several other Hydro-Max systems. One on a Ford medium duty had a saginaw pump very similiar to mine. I grabbed a high pressure line from that and LUCKILY got to thinking about the the output of the pump and pulled the guts out of the output fitting that controls the volume and pressure out of the pump.

I pulled those parts out of my Chevy Saginaw pump and visable they were identical. Looking more closely and comparing hole sizes with a drill index I found that the Ford pump was outfitted factory with higher pressure and more flow out of the pump by several drill sizes larger. I put Ford Saginaw application stuff into my Chevy application pump to boost it's performance and try to maintain as closely as I could a matched system.

Tonight was my first test and WOW was I happy with the results. When backing up and nailing the brakes it feels like the front completely unloads and you stop NOW. A couple of frozen driveway tests has it pretty easily locking up all three axles and sliding to a stop...which is nice for an 18,000# truck.

Bjorn and his helpful quest for deuce truck knowledge at one point put a pressure gauge on the brake system and posted his findings, iirc, to be 1800psi line pressure locking the brakes. Hydro-Max is supposed to put in excess of 2100psi. This system also has a back-up electric motor pump (in place of a nitrogen charged accumulator like the H-boost) that will give you brake pressure when the engine isn't running. I'll post pics later today when I'm back at my computer.

RE: Hydro-Max Brake Assist (long read)

Where are the pictures for all the reading I was expecting to see what it would take to put this on my deuce or perhaps a better candidate, myt M 52 which has power steering. I know your truck has much more going for it with the CAT but could I do this with my truck?

By the way last one in the office so the read was not too long at all.

RE: Hydro-Max Brake Assist (long read)

Sounds great.

Might want to keep the air compressor and tanks (new if they are rusting on you), it is nice to have onboard air.

Do you plan on trailering anything? Just thinking of air or air/hydraulic trailer brakes.

RE: Hydro-Max Brake Assist (long read)

I'll have pictures up in a couple of hours. I ended up finding a nice York air conditioning pump, the kind that are easily converted to onboard air systems, and mounted that where the old compressor was. Don't have it plumbed yet but that will give me on demand onboard air. I still have one of the factory tanks (rusted one conveniently got pulled when crane went on) and I have another tank mounted behind the cab that's 30 gallons...I think. I have two of them mounted but use the lower one for the hydraulic oil for the crane.

I think this system is easily adaptable to these trucks with the exception of the pedal assy. I originally mounted the hydroboost system under the truck nested up beside the transfer case. The Hydro-Max unit had a much larger (wider) reservoir so I firewall mounted it. Room was a little tight but it ended up fitting pretty well. Hood clearance is on the 'just barely' side but it does clear. Although these systems can and are installed with the booster and steering off of the same pump, the several trucks I had looked at with this had seperate pumps for steering and braking.

Trailering...yes, I have thought about that and if it becomes something that I feel I will definately need, I'll get an air valve from a straight air brake truck and make some linkage to it.

RE: Hydro-Max Brake Assist (long read)

whats funny with this is we have a ford F750 potato truck with that system and we hate it I spend hours
every year making it work for the potato season and the deuces other farms have never seem to lose brakes.

RE: Hydro-Max Brake Assist (long read)

Your's is more complicated because it goes thru some other things in it's factory form. Mine is pump, booster w/master cyl and return to pump. Here's some pics-

RE: Hydro-Max Brake Assist (long read)

I know I'm a little slow here, so how did you get the brake rod installed? It looks like that system will need a hanging pedal to work it.

RE: Hydro-Max Brake Assist (long read)

Good call Gimp...I hung a pedal. Got the pedal assembly from the International S1700 the booster came from. I made up a mount that bolts onto the stiffener between the firewall and dash at steering column. Reinforced it all with angle iron top and bottom, it's very solid. Spent several hours of a couple of days laying on my back wedged inbetween the seat and pedal working under the dash with my legs propped up on the open door. That sucked. Sort of all of a sudden last night I realized I was ready to fill the pump and test it. The pump picture didn't come out well enough to post. It is located under the York pump...that is what the funnel is there for. It's mounted on some modified Big Block Chevy PS mounts.

RE: Hydro-Max Brake Assist (long read)

very nice job . glad to see all of that hard work pay off

RE: Hydro-Max Brake Assist (long read)

Just a quick update on my Hydro-Max brake system...was a little surprised not to hear from a couple people about this updated system so thought I'd follow up. It is working absolutely flawlessly and I could not, in any way, ask for it to perform any differently or better. Pedal feel, travel, simplicity of the system (aside from pedal mounting), and just the all around way it handles the truck is just great. I've been doing some hauling lately with the truck with a GVW a little over 32,000 lbs combined it doesn't really care that there's a big load. Have put about 250 or so miles on it-

RE: Hydro-Max Brake Assist (long read)

Good deal Tom, glad to hear the work was not wasted. Nice to know we have options.

RE: Hydro-Max Brake Assist (long read)

I'm in the middle of adding a hydro max to my old chevy school bus. The MC died, and I was at the pick-n-pull, saw one, and am replacing the old MC with the Hydro. I just had to shorten the pedal rod. the biggest step now is plumbing it from the PS pump to the hydro max, and back down to the steering gear.

Try and get the pump or if they're both Saginaw pumps, pull the outlet fitting, pressure valve and spring all out of the original H-Max pump. I found that pump to have more pressure and flow then a 3/4 or 1 ton pump. *most* of the ones I had found ran seperated systems for brake and steering, but some were in line, like normal, like you're planning on doing. I think you'll be REALLY pleased with the results- I sure am.

The system I got was off of a '97 S1700 International so it's a fairly new system. Another reason I went for this set up is that it's relatively CURRENT technology, very simple with three main components (pump, booster, MC...2" bore btw), have full brake pressure immediately after engine starts, and is rated 20,000 lbs GVW over what the deuce is on-road max rated. Sorta like using a Grizzly .50 for rabbit hunting.

Looks like another successful combination of big parts, smarts and old trucks Tom. Good job.

Tim, I'll look for those parts today!!! Had a deadline to make the brakes work and was busting my hump to get them going-

spicergear said:

......This system also has a back-up electric motor pump (in place of a nitrogen charged accumulator like the H-boost) that will give you brake pressure when the engine isn't running.....

Click to expand...

Great job Tom, always interested in different solutions!
Was going to ask about the back-up in case the engine shuts down and found the answer above. Is the electric motor automatically cutting in when the pressure drops? Would that motor/pump be suitable for an engine pre-lube system?
What is the pressure rating of your return circuit?

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

Is the electric motor automatically cutting in when the pressure drops? Factory wiring has the electric motor on a relay with a couple different triggers...if I've understood the literature correctly. Engine off, key off, press brake and will turn on. Key on, engine off...turn on. Engine running...stays off. Engine stall, turn on. <--when I say 'turn on' that means it is 'armed' and will turn on when brake pedal is depressed.

What is the pressure rating of your return circuit? This I'm not sure of. These systems, in certain applications, run high pressure down to the steering gear after the booster unit. Other applications run the steering gear on it's own pump so the return is simply right back to the pump reservoir. Mine is this style. Factory set up used standard 1/2" Fuel and Oil hose so I did too. I made that part so I could take advantage of both returns into my pump reservoir. I figured that two 3/8" lines shouldn't be a restriction coming from one 1/2" line. It probably doesn't matter since high pressure PS box lines can be put after the booster but it's how I wanted it so I wouldn't have any concern of changing the factory return flow.

Would that motor/pump be suitable for an engine pre-lube system? May very well be! Obviously it should be able to handle the temperature change from start up to operating temps as circulating oil in PB/PS systems is going to carry some heat with it. The system is stated to be able to put enough power to the booster, via the elec motor, to make 600psi line pressure in the brakes when applied by the pedal. I don't know if one can supposed-math this out but stock hydroboost setup run 1100-1400psi application depending. My pump is supposed to be in the 1200psi range but I increased that with the pressure cartridge from a medium duty truck's pump. So pressure is up maybe 1500-1600psi.?.and making 2100psi max line pressure. 2100psi (line pressure) divided by 600 (line pressure elec motor) = 3.5. Now take 1500psi (est pump output) / 3.5 (line pressure calc result) = 428.5psi estimated output elect motor- ?? You may be able to simply put it on a push botton and 'blip' it until the oil pressure is up to where you want it. Motor has a simple two bolt flange and it looks like a simple adapter plate with the fittings you want could be very easily adapted to this. Neat idea Bjorn-

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

OH, and the elec pump motors can be purchased in 24V.

It appears to be a dual reservoir master cylinder. How did you split up the brakes? Would the smaller unit work for a bobbed deuce with two fewer brake cylinders to activate?

Spicergear, I've never seen one of these plumbed with high pressure out of the hydro-max booster to the gear. I've always seen them either isolated, or in series of pump to gear, gear to booster, booster to tank. The pickups used to be in series, pump to booster, booster to gear, gear to resivoir, and the booster had an extra low pressure return line for a total of two return lines to the pump resivoir. Maybe (definately?) I havn't seen all the applications, but check carefully if you have any intentions of multiple items being driven by this pump.

I'm kind of curious as well as to how you split the hydraulic circuits. Was your unit from a donor with six brakes? I've never laid eyes on one, but I have heard tell of such a unit. The rears on our single rear axle systems are typically very strong anyway, it seems like the rear would be crazy strong if you set a four brake unit up to run two fronts and four rears.? Very curious. I don't think I'm headed this way any time soon.

JasonS, having much experience in hydraulically boosted brakes, from 3/4 ton to 25,999 I would have to strongly recommend you stay out of the pickup trucks when you're looking for parts. I'd call these systems "adequate" but definatly not outstanding in their 3/4 and one ton applications. Hydro max units are not that different on paper, but are a much more stout and reliable unit, and strong enough for your application. Ford Superduty stuff is good too performance wise, rated well over a fully loaded non-bobbed deuce, but newer (expensive) and in my experience the durability is not on par with the medium duty stuff. Basically, look for a donor with a hood that tips forward.