Hydro-Boost upgrade

[mineral co]

Hello Folks,

This is my first time posting on an FSJ forum, but I think I've done enough reading to, hopefully, make some of my initial questions less annoying.

I have had my '84 GW since '95, but it hasn't been touched since '99. For various reasons, I am waking it up again and it will become my daily driver. I live in SW Colorado, so the ol' girl will also do double-duty as my off-road driver, though I don't intend to do any extreme stuff. However, you never know for sure what you might encounter that you can't back out of.

The brakes are not what they used to be! Firstly, the pedal goes about half-way down and then firms up okay. To me, this says the master cylinder has a seal in either the front or rear circuit that is letting fluid past, so it's time for a new master cylinder.

All my automotive experience is with a certain German mark, and a situation like this would say that it is also appropriate to go through the calipers and wheel cylinders, and replace all the brake hoses too. That's all well and good but, at best, that brings me back to the stopping power I had a dozen years ago. Back then, I never considered the GW's brakes to be inadequate in any way but most of my driving was highway, with only very light off-roading.

Here in Mineral County, even some of the common and basic routes can hit 20 degrees, and one popular one is closer to 30 degrees. I think I want a bit more confidence in the brakes. Towards that end, the Hydroboost seems to be the easiest way to get brakes I can sit on and stay where I'm at without killing myself (figuratively or literally!).

Having done all the reading and having planned a trip out to the valley to get some other parts for the ol' girl, I decided to stop at the one wrecking yard in the area to see if I could find a Ford TFI coil bracket. And, it couldn't hurt to see what else they might have. I did find a coil bracket, and learned that there is more than one type of Ford bracket. This one is from an '88 PU 5.8 and has an ear which should let it sit in a good orientation while still using the single manifold mounting bolt. And then there was that '95 Astro Van with the hydroboost.

The proprieter gave me a reasonable price for the unit ($75), so I am very interested. Now the question(s).

Depending on what posts and sites I've read, some say they used the unit from the Astro Van and some say they have used the unit from larger PUs and vans. What is the difference between these units (is there a difference, even model numbers)? Do I care about the differences? Since I am planning to replace the front calipers anyway, I am seriously considering the larger JB7/JD7 units (15% larger piston diameter). With the hydroboost, I can stay with a larger diameter MC to keep pedal travel short and not worry about an increase in pedal pressure.

Is there a rebuild kit for the Hydroboost? Are these units at all problematic? Is it better to let the expert rebuild and checkout the unit, or do they just "work" even straight from the bone yard?

I read a post with a man answering the question of another poster, saying that there were NO "engine-off" stops available with the Hydroboost. This must be incorrect, right? After all, that is what the accumulator is for, is it not? I noticed on Elliott's site that he has (or had, anyway) the long version of the accumulator available. Does this one accumulator work on both versions (if there are two) of the Hydroboost, or is that version-specific?

And, lastly, what all else needs to be grabbed from the donor vehicle besides just the HB unit itself? Whether they would work or not, it seems smart to at least grab the supply and return line. Is this necessary?

Thanks!

Chris

[mineral co]

Well, it's been a couple days since I made the original posting here.

There have been no responses, but there have been a fair number of reads. That indicates that there is definite interest in the subject, but other folks may not have been able to learn anymore about the system and conversion than I have.

There are many, many internet locations describing how to make the conversion to a wide variety of different types of vehicles, but I haven't found much of anything related to the technical considerations that may apply when selecting a particular unit. One thing I did read somewhere is that there ARE two different versions, but the differences are related to how the accumulator is implemented on the unit. So long as the accumulator works and has a reasonable capacity, it has no other bearing on what version of Hydroboost unit I might select.

Reading everything about Hydroboost on the IFSJA site I got the distinct impression that these units were used on a fairly select group of vehicles. i.e. Astro Vans and some GM PUs. As it turns out, this impression is not correct. They aren't even limited to GM vehicles.

Somewhere, I read something stating that this system was even used on later model full size Ford trucks. Really? I have an '07 F-550 PU with great, huge brakes. Time to go have another look at the truck.

Pop the hood and have a look. Sure enough, Hydroboost.

Whada ya know.

What I as surprised at was the relatively small size of the unit. I really think it is the exact same size as the unit I saw in the bone yard '95 Astro Van the other day.

This is what I do know: that truck weighs more than 8000 pounds, and I have put 24,000 pounds worth of trailer and cars behind it (the truck has a 33,000 pound GCWR) and that truck will stop!

The most common comment from people that have done this upgrade is that you can put people up against the windshield if you're not careful. The third most common comment is that it lacks the "feel" of traditional brakes because there is relatively little pedal travel or foot pressure between calmly slowing down and sliding down the road. I think these are legitimate considerations, especially if somebody else might be driving the vehicle on occasion.

My '67 big "German" car weighs more than 5400 pounds, but in typical German fashion, it must still perform like a sports car. They did two things in particular to insure it would stop. First, each of the front wheel brakes got two calipers, and they used a power brake unit not unlike the Hydroboost, except that it operates on compressed air rather than hydraulic fluid. The vacuum boosters used on the other models of this same make had pressure amplification factors of either 3:1 or 4:1, depending on the model. The pressure booster used in this model has an amplification factor of 25:1!

And, unlike the other models, this car has very sensitive brakes with the exact same concerns as the hydroboost (but, WOW, it will stop!). Knowing what this feels like (and how potentially dangerous this is to the unaccustomed occasional driver), I would like to find some way to get around this "problem". And that brings me back to the F-550.

I had no idea until last night that my truck had Hydroboost on it. Based on the pedal feel and travel and the comments from those who have done this upgrade, I also would have had no reason to suspect that the truck had Hydroboost. The truck actually has a longer pedal travel on it than other vehciles I've driven. It was like this even when it was brand new, and I had some concerns about the correctness of this and mentioned to the shop man at the dealership. He said this was typical and normal for the truck.

It didn't take long before I concluded that Ford really did have a better idea because the longer pedal travel and progressively increasing foot pressure required to get that was much easier to drive and made controlling heavy trailers ever so much easier than my prior trucks. I have come to believe that this really is an improvement over shorter stroke pedal systems.

So, how is this accomplished even though there is a Hydroboost? I don't know the answer to that yet, but it almost has to mean that the newer Hydroboost systems have been functionally modified from the earlier systems to allow a longer stroke. The truck's system is still just a peddle-booster-MC system. If this is actually true (the functional modification), then that means that there is a better (and safer) choice for upgrading to Hydroboost than what has typically been used in the past.

More to come. . .

Chris

[srobertsfsj]

Hi Chris,

Im sure other will chime in soon, its summertime so many take a break from the forum because they are out doing stuff. I have hydroboost on my waggy and I love it but I think the biggest difference with my build was when I put rear discs on it. I can stop on a dime. Something to consider. I bought my hydroboot setup from Elliot so I cannot talk techinally about it.

[whsii]

http://www.txfsja.org/forum/viewtopic.php?f=13&t=74

This is Elliott's add on The Texas FSJ board. He is probably as good a source on information and parts relating to Hydro boost as anyone regarding FSJ's.

If I were going to go Hydro boost, I would totally rebuild all four corners and replace all rubber lines. Inspect all steel lines and replace rusted ones, or better yet all.

Just my thoughts...

[Tad]

...If I were going to go Hydro boost, I would totally rebuild all four corners and replace all rubber lines. Inspect all steel lines and replace rusted ones, or better yet all.

Just my thoughts...

This is important when going HB.
All your components need to be in tip top shape.

I am not a HB guru, I barely understand the process but have been running this way since 2006.
When we get into big tires, lower gears, etc. these rigs get a little harder to stop, especially in low range coming off of steep hills.

I won't bother with the details of my system since it's easier to do on a 74+ rig and whsii is correct, Elliot is the person who did the leg work and research to make this a painless and common upgrade.
I will address two items:
1.
Yes, I can put you into the windshield if I was dumb enough to let someone ride in my jeep without a seat belt.
2.
There's this comment that gets tossed out sometimes that goes..."you have three good pumps if your engine dies".
Not my experience at all. You have one good pump, when you go for number two you are essentially manual brakes now. You will feel stopping power but with less than desirable results.
(I tried it on a long flat vacant dirt road just to know what to expect)

[mineral co]

I've learned a bit more over the last couple of days, with help from Elliott and a few other folks.

First, Elliott said that the reason for the more progressive pedal action in my Ford truck is due to it having ABS and has nothing to do with Hydroboost. Without something to provide a place for brake fluid to go, the system is just going to come on fast, and that's just the way it is.

Differnt sources of Hydroboosts, 1 Ton Chevy PUs vs. an Astro van, for example, do have different mounting bolt patterns but are, presumably, the same in other respects.

Where does that leave us? About the only thing left is how many stops you get after the engine is no longer running. And that becomes somewhat interesting.

Elliott said that the accumulator starts at a 1500 PSI gas charge, so the pump has to supply more than 1500 PSI or nothing happens and there is no reserve once the engine is off.

Okay, that's good to know. In reality, you would need a pump that created quite a bit more than 1500 PSI in order to store any kind of meaningful reserve. A 1600 PSI pump wouldn't get you much. So, dig out the FWSM and see what the steering pump pressure is. Figures. The regulating valve is set to 1500 PSI. So if everything is operating perfectly, you have no reserve. Chances are most of our pumps don't make the 1500 PSI any more anyway.

So why are some folks noticing that they DO have some reserve? There is only one way to store fluid in an accumulator, and that requires the fluid pressure to be higher than the static pressure of the gas charge in the accumulator. There are two cases we can create to make this happen. Either you increase the pump pressure, or you decrease the pressure of the static gas charge in the accumulator.

Gas charged accumulators leak the gas. It's slow, but it is inevitable and it can happen even in a brand new item just sitting on a shelf. Normally a leak is bad but, in this particulalr application, it may well have its benefits.

If, for example, enough gas has leaked off that the static charge is down to 1100 PSI but your pump has only fallen to 1300 PS, you are going to store a reserve of fluid in the accumulator and have some use of your brakes after the engine is off. Fascinating, isn't it? It's rare that a fault actually improves performance.

In my case, I do want to have that reserve capacity, and the bigger the better, but I'm not about to go around bleeding off gas from accumulators to achieve it. That only leaves cranking up the pressure from the pump to something quite a bit higher than 1500 PSI, but I have no desire to start blowing seals out of my pump or steering box.

I need a different pump. Actually, what I need is an additional pump. One that can generate, say, 2000 PSI. That would give me a fair reserve.

So that is my decision about how to go forward with this. I'll run a second pump for the Hydroboost and leave everything in the steering system alone. It occurred to me that the easiest way to get a pump that would be well matched, pressure wise, with the Hydroboost would be to get the pump from a donor vehicle that had the same Hydroboost. I have access to a new Hydroboost for a '95 Astro/Safari, so I shoud get a pump from an Astro/Safari. And, as fortune would have it, Elliot did a second pump mounting designed around an Astro pump.

This isn't the cheapest way to Hydroboost, but its not much more expensive and it has the two benefits of always having a reserve in the accumulator and nothing is interacting with the steering. And it answers one of the original questions about what to get when stripping a donor vehicle: get the Hydroboost, MC, hoses, hardware and the pump and associated mounting bits.

Chris

[AwesomeJ10]

My two cents is this;

I recently converted my '88 waggy to a rear 14bolt with 3/4 ton disk brakes. Also has a D44 HP up front with 1 ton dual piston calipers. Otherwise stock braking system; stock vacuum booster, stock master cylinder, stock lines, stock proportioning valve. Very simple system.

The braking power is absolutely incredible. I couldn't imagine having more powerful and responsive brakes.

I have absolutely no doubt the brakes will perform awesome in Ouray next week.

[jaber]

When I did mine, I drove for over 6 months not realizing I did not have any rear brakes. It was such an improvement, just the fronts under HB power would slow my truck down faster then the stock system. My truck weighs in just under 6K with tools in the boxes.

[mineral co]

As if trying to understand FPL (female-pretzel-logic) wasn't enough to make you bang your head into a wall , try getting even the slightest technical info out of Bosch! Even the corporate headquarters has asked me to not call back.

I have learned that there are at least 20 different models of hydroboost. These not only have different nitrogen charge pressures in the accumulator(s), but different pressure piston sizes and this is what I am most interested in as this is why Hydroboosts from different vehicles behave in widely varying ways. Bosch won't help me get a model number unless I give them a model number.

Does anybody have an inside contact that might have any sort of access to this information?

Thanks,

Chris

[whsii]

Again, Elliot is the Hydro Boost Guru of FSJ's in my opinion.

[mineral co]

Elliott and I have discussed this subject at length. We are beyond what either one of us knows.

Believe me, I wouldn't be going after the big guns without reason.

[mineral co]

I found this on the 'net. It's a pretty good starting point for an education on the Hydro-Boost.

http://www.gobookee.net/get_book.php?u= ... Npc3QgLi4u

Chris

[mineral co]

I am pleased to have the Hydro-Boost now installed and working!

I couldn't find some of the answers I wanted prior to collecting parts, so I decided to just do something and see what the effect was. I decided to use the smaller bore unit from a '95 Astro van as it's operation would be less extreme than going with a larger bore unit, just in case. This was readily available without laying out a lot of money, so this made sense to me.

I also wanted to replace the master cylinder just because the one on the truck was original and nearly thirty years old. In anticipation of also goiing to the larger JB7/JD7 brake calipers up front, I decided to go ahead and go to the somewhat larger bore master cylinder from a C30 Chevy truck. The stock master cylinder bore is 1.125" and the C30 master cylinder is 1.250", right at 10% larger which translates to about 10% less fluid pressure being generated.

I have not yet swapped the front calipers to the larger units, so my current system is operating less effectively than it would be if I had stayed with a stock size MC, and it's still very effective! Locking up the tires on pavement is now no problem whereas, with the same setup and the vacuum booster, sliding them on gravel required real effort and sliding them on pavement was impossible.

So I have all new brake hoses, properly adjusted drum brakes, 100% replacement of brake fluid and a good, high pedal, new MC, but stock cylinders and calipers, and what ever pads and shoes it had before I bought the truck 18 years ago.

I'm going to drive it like this for a while before swapping to the larger front calipers, just to make sure I don't get unnecessarily carried away with things. I am a bit spoiled by my '07 F-550 (that has factory Hydro-Boost) as the brakes are very effective and require very little force to operate, and want to immediatly make the GW feel the same way but surely I can be patient for a week or two.

The larger calipers have a ~15% larger piston so will generate the same force with 15% less fluid pressure, and I think that is going to turn out to be a very good combination.

Thanks for the help!

Chris

[mineral co]

I have had many, many other tasks to take care of on my truck so I've only recently gotten back into the brakes.

I've been driving the truck with the Hydro-Boost for about two months now, and have gotten used to how things are working. Whereas adding the Hydro-Boost made a substantial improvement, and made it possible to slide the tires on dry pavement, I've come to feel as though things still required more pedal effort than it should.

As part of a trouble-shooting exercise to find a bad vibration after installing a 4" spring lift, I had completely removed the brakes at the left-rear wheel and plugged the line. Not only did it have zero effect on the vibration, it had a noticeable negative effect on the truck's stopping power. This was more than a bit surprising as rear brakes just don't contribute all that much to the total braking ability on a properly working total brake system.

As part of this whole exercise, I also wanted to increase the size of the rear wheel cylinders a bit to see what effect it had, but only after changing the front calipers to the larger JB7/JD7 units. Because I had to re-assemble the left-rear brake anyway, I decided go ahead and put the larger wheel cylinders on even though the front calipers hadn't been swapped out yet. The stock wheel cylinder size is 15/16" and the replacements are 1", an increase in size of about 6%.

This had a very positive effect on the overall braking of the truck, reducing pedal effort a lot. Again, this was surprising as such a small increase in the size of rear wheel cylinders just shouldn't have that much impact. Regardless of anything else, for making such an improvement with such a small change in the rear brakes, I can only conclude that my front brakes are not working nearly as well as they should.

The stock front calipers are working and the rotors are in good shape, so I'm of the opinion currently that the pads must just be crap. In order to make as good a study as possible, the current front pads should be changed to the same type of pads I'm going to use with the larger calipers (MKD153) before swapping to the larger calipers, but that isn't going to happen as there are too many other things demanding time and money right now. The larger calipers are about 15% larger than the stock calipers, so, all other factors being equal, there should be a very noticeable reduction in braking effort, but it shouldn't be substantial. If it is, then I'm going to believe that adding the modern type pads is responsible.

Hopefully this swap will happen in the next week, and we'll see what happens. I'll post up afterwards.

Chris

[SJTD]

That was more like a 14% increase. Gotta work with area not diameter when figuring force applied by a piston.

Are the fronts still locking first?

[XJChad]

Great info, thanks! Im going to be doing this soon on my '89 GW, as funds permit.

Sent from my SCH-R970 using Tapatalk

[mineral co]

That was more like a 14% increase. Gotta work with area not diameter when figuring force applied by a piston.?

You are correct!

I calculated all this stuff out a few months ago to determine what size I wanted to go to, but failed to do the complete math again when I made that post earlier today. I like accuracy, so I appreciate your pointing that out.

Are the fronts still locking first?

Just barely. The truck stops so hard with the new BFG AT T/As that I can barely keep my composure when doing the stops. I switched to dirt roads to do that particular test.

[sgtpoliteness]

Great thread! Subscribed!

[Southern Gorilla]

I switched to dirt roads to do that particular test.

Don't!
Testing brakes on a dirt road will not tell you how they will react on pavement. The reduced traction means less weight transfer under braking. Which means the rear wheels will carry slightly more of the load on dirt. It also means the front wheels will lock up first since they aren't under as much pressure as on pavement. So if you adjust things to get them locking up equally on dirt you will find yourself with underpowered front brakes on pavement and rear wheels that lock up quicker as well. Test under the conditions you expect to operate under.

Of course, if you have a proportioning valve you can adjust on the fly from the cab then testing on dirt will tell you which setting to use on dirt. That's actually a fun idea. You could have different settings based on whether you were empty, loaded, trailering, on dirt, dry pavement, wet pavement... I think I just added something to my build list.

[mineral co]

I switched to dirt roads to do that particular test.

Don't!

I'm not adjusting anything! As clearly noted in my post, this is a temporary state until I get the front calipers swapped out in the next few days.