Not so, 460 vans had it too.

 

Sounds like a trailer brake controller.
The hissing is coming from a leaking brake booster.

 

I use the truck mainly for snowplowing my property. I put less than a 1000 miles a year on the truck. Not sure if this device is on because I have a myers plow installed or not.

 

If you blew a brake line you need to re-center the proportioning valve's piston.

Check the info in this thread;
https://www.ford-trucks.com/forums/1...ing-valve.html


Your booster's still leaking.

 

My 1985 F150 has the same thing under the dash with the red light...
When I didn't hook that back up on mine when I installed my new master cylinder/break lines/etc.

When you tried to bleed the system did you start with the passenger side rear bleeder screw? Then driver side rear... then passenger side front... then driver side front? I learned that you are supposed start bleeding the system at the farthest point from the master cylinder and work your way to the closest.

 

Ya know, I still don't know how to bleed the damn thing on an F350.... I loosen that nut
some but it starts leaking fluid so I stop, I'm afraid of opening it too far and having springs
or BBs or something fall out (I can see it now..... "Ah, sh3333333tttttt....") and I wouldn't
have the slightest idea how to correctly put it back together, thereby leaving the truck
unmovable until I figure something out.

 

But you DO have the instructions for an F-150.


Hijack complete!

 

On other sites, I read of it being necessary to swap out the pedal assembly when doing a hydroboost conversion; is this a year-model specific thing or using wrong year-model parts or what ??

I also have read of several Ford guys using GM hydroboost units with great success; are the GM units as straight-forward to install as the F-SuperDuty unit used by the initial poster ??

Is there a list somewhere of which hydroboost units are a bolt-in affair and compatible with our stock brake-pedal ??

I know it's a lot of questions; thank you for answering them.

 

I put the GM Hydroboost in my Jeep Wagoneer last year after doing a ton of research. I learned a number of things, but not everything I wanted to learn.

Bendix originally designed and built these systems but sold the product to Bosch at some point and will no longer provide support on it. They will refer you directly to Bosch.

I have never been so frustrated as I was trying to get any info out of Bosch USA. The circle jerk continued for hours. They may well have some technical information on these things, but they don't know who inside the company has it. What a PITA.

What I do know is that there are many different versions of the Hydroboost, but I don't know what the differences are! What I really wanted to know is if there are different boost ratios or different required hydraulic input operating pressures. I still do not know this.

At some point you just have to try something.

The Jeep and other early 4WD guys frequently use a Chevy Astro Van unit. The '95 model year seems to be what is generally referred to but, as far as I can tell, all Astro Vans used the same unit. I did easily find exactly that at the closest bone yard here.

In order to use the Astro Van HB unit "as is" on a late FSJ (full size Jeep), you have to add a 1" spacer between the HB mounting plate and the firewall, but other than that it's a piece of cake. The bolt spacing in the Astro
HB plate is exactly the same as the FSJ firewall, you just need some slightly longer bolts.

However, it's not always that simple as other firewalls have different mounting hole positions and/or the booster is offset from center by more or less. What this means is that there is a myriad of different mounting plates/spacers required, depending on what the HB unit came off of and is going on to. The good news in that department is that their are people out there that have already done all the research and designs and have "off-the-shelf" plates and spacers for just about anything.

A handy person could easily make these items themselves, except for one thing and that is that dang special nut that holds the HB unit to the mounting plate. It's some king of special Kelsey Hays thing, and not cheap. That problem, by itself, says that you either need to find a standard HB for your particular application, or you need to work with one of the guys that has already figured out how to do the non-standard conversions and follow their advice and use their parts.

At least as far as Bullnose Ford trucks go, it appears to be a very simple conversion if you start with a HB unit from a '97 or earlier Super Duty truck. The mounting plate is already the right type and the rod is the right length (HB units from other makes/models have different rods, and this might account for why there are so many different models of HB). Buy the power steering hoses for the donor truck and that becomes a bolt-up affair as well.

There does seem to be some discrepancy in the required pump-to-HB hose. I found two different Edelmann numbers for this hose (71415 and 71422), but I think this may be related to different generations of PS pumps. The HB-to-steering box hose seems to be consistent in all '97 and earlier years (Edelmann 71416). I bought both of the pump-to-HB hoses (they're dirt cheap), so will find out which is appropriate for my '86 Bullnose.

I read in the OBS forum that the part number on the HB specific brake pedal for the manual trans is "E7TA-2455-xx". My truck has the "E4TA-2455-xx", which seems to have less pin offset in it than the standard brake pedal used in the OBS trucks, but is still greater than the "7" pedal. I'm not certain that the OBS "7" pedal will fit in my older Bullnose truck, but the part numbers are so similar that I'm optimistic that it will. I bought one this morning and will find out once it gets here. Note that the pedals for a truck with an automatic trans will have different numbers.

There are different generations of HB, regardless of anything else. The very earliest units have a spring type pressure accumulator. These go all the way back to '70s Cadillacs, and I'm of the impression that these units should be avoided completely. Anything after that period will have a nitrogen accumulator, and there are at least three different versions of it. The color (and perhaps the length) indicate the differences, but I have not been able to learn what the differences are. There is a silver and a gold anodized unit, both the same length (about 3.5"), and (I believe) the only difference is the initial nitrogen pressure charge. The gold unit is far more common than the silver. There is also a long, blue colored accumulator, but I've seen it only in pictures. At a minimum it would provide a larger reserve, but I know nothing about it's pressure.

Accumulators do go bad. There are special tests that can be done to check the pressure in the accumulator, but these are way outside the scope of most folks. Unless you are buying a new unit, you don't know what you are getting in that regard. You "pays your dues, and take your chances". The one definitive test is that if you can wiggle the accumulator while mounted to the HB, the accumulator is dead.

If your power steering pump is in good shape but you have no reserve (or only little reserve) braking after shutting of the engine, the accumulator is bad. Accumulators can be replaced but, unless you're really familiar with hazards of working on hydraulic accumulators, don't even think about taking that unit apart. You don't have the means to recharge it anyway.

GM HB units generally use metric fittings, but earlier units are available with standard inverted flare fittings. Have a look through RockAuto's booster descriptions for an early '80s K30 as most descriptions include the fittings thread information. Mid '80s and on will all have metric threads for the fittings. This is not a deal killer as metric HB specific AN fittings abound, so you can make up what ever you want however, from what I've seen, using AN fittings and hoses gets expensive real fast, especially if you want to use SS hoses!

You have to pay careful attention to the rod between the HB unit and the MC too. Most GM HB units have a dimple in the MC end, much like the dimple in the MC, and there is a floating rod between the two units. If you don't get this floating rod, you are going to do nothing. From what I can tell on the '97 and earlier Ford HB unit, the correct rod is part of the HB unit so you get to skip this concern.

Just as with the Ford unit, there are different MCs available for use with the GM HB. If I remember correctly, the MC from the Astro Van is 1-1/8" in diameter, where as the 1 ton trucks will use a 1-1/4" MC. Whether the GM and Ford HB units have the same MC mounting hole spacing, I do not know yet.

I do know that HB units from different GM vehicles will have different pedal rod lengths, and different offsets in the rod too. The diameter of the pedal pivot pin hole may vary as well. In most cases, the rod is not hard to remove so, if you feel the need to do some welding on it, remove the rod so that you don't have to worry about conducted heat damaging any seals in the HB unit. Some GM units have the rod staked in, and those rods don't come out.

The HB unit is a sophisticated, tight-tolerance unit. Most PS systems are not. For this reason, you need a clean hydraulic system! At a minimum, replace all the steering fluid in the system and add a good PS filter. I would do this well in advance of installing the HB unit so that the filter has the best chance at collecting any metal particles that are still in the system and not get them into the HB unit. Cardone has the Magna-Pur filter with a magnet in it, and that is what I'm using.

I saw it somewhere that when using a "T" in the return line that the HB unit should be a "straight-through" shot, and the return from the steering box should come into the side port of the "T". This is not correct! The steering box return MUST go straight through, and the HB return must come in on the side port of the "T". The reason for this is that fluid is always being pumped through the steering box (even when the HB is in place) and relatively high flow rates. If the steering box return line is brought into the side port of the "T", it then hits the wall and has to turn 90 degrees to get back to the PS fluid reservoir. This creates some back pressure on the other "T" end, which is the return from the HB. This has the nasty side effect of pressurizing the return at the HB and it will cause the unit to operate lightly and drag the brakes!

When not being operated, the HB just passes the fluid from the high-pressure input directly to the outlet port going to the steering box input. Even when operated, the fluid return from the HB is only a very small squirt and generates no back pressure to the steering box. If you replace the existing PS pump reservoir with the unit from the SD, then you have two return hose nipples and there is no problem with back pressure to the HB, plus it makes routing hoses a lot cleaner and simpler.

The pump's pressure has a direct correlation to the effective boost the HB can create. If your pump is weak, you will notice it at the brake pedal. GM pumps run at about 1200 PSI. I don't yet know what the Ford pumps run at, but if it's significantly less, then you'll have to consider the best and easiest way to bump it up. The HB can easily accommodate a supply pressure of 1500 PSI.

And, on the subject of pressure, a properly operating HB can create brake line pressures over 2000 PSI (I've seen measurements of 2500 PSI!). Think about that for a minute... You brake system has to be in top-notch condition in order to work safely under those conditions. The rule is to get your brakes in perfect working order BEFORE installing the HB. HB is not a substitute for good brakes, it is a way to enhance otherwise good brakes. At an absolute minimum, replace all the flexible brake hoses! (This should be done every ten years, or so, anyway.) This is where best-quality SS braided lines are appropriate as they are generally rated for a working pressure of 3000 PSI.

Another note about those pressures: Cunifer lines are very popular for hard line replacement, HOWEVER Cunifer lines have a max working pressure rating of only 1600 PSI. A HB unit may go way beyond that, so think about that if you are replacing hard lines too.

Sorry about the very long post, but it just seems important to put all that out there.

Chris

 

Now you have me seriously considering this upgrade. My vacuum tree was accidentally damaged in the engine install, but I can run off the carb for a bit. I also plan to do a lot of towing, in excess of 4000lbs on a regular basis.

So simple question. What other upgrades, besides the SS lines and HB system would be appropriate for a tow vehicle, especially with the HB conversion?

 

Good! You'll love it.

One of the great things about HB is that it is a "stand alone" upgrade. There are lots of other things you could do, but you don't have to do them all at same time as the HB. On it's own, having HB just means that you don't have to press on the brake pedal as hard in order to generate the same amount of braking force. It' "old man" friendly in that regard.

However, if you are pulling a trailer or just get into a panic situation, you can generate a lot more braking force than you can with a vacuum booster. You don't get so worn out try to haul down 10,000 lbs when you're on the brakes a lot.

Now, bear in mind that all we have done is make it easier to operate the existing brake system. The brakes themselves are the same as they were before. If you know you are going to be taxing them with significant loads, then an upgrade to the brakes themselves should probably be looked into.

My truck is an F-350, so it's already sized to be hauling large loads. The brakes are substantial enough that, other than making sure they are working as intended, there is no need to "upgrade" them. If the tow vehicle is going to be used beyond its design rating, then you really should look into beefing things up quite a bit (like trading an F-150 for an F-250 of F-350).

From your user handle, I'm going to assume that you have an F-250, so pulling 4,000 lbs shouldn't create any large concern so long as everything is working properly. The roads you expect to drive may be a factor. If you mostly traveling on the Interstate highways, then there are only a few places were you would have to be careful. If you're driving steep mountain passes on a regular basis, you are going to want some heat tolerant rotors and pads.

I just finished installing the HB unit this afternoon on my F-350. I'll explain why in my post on that exercise but, for now, I'll just say that you MUST address the HB-rod-to-brake-pedal-angle-issue as part of the project. Replacing the brake pedal is the fastest and simplest way to do this.

I got this '97 Superduty HB unit (model BRB37) brand new from RockAuto this week for a very inexpensive price ($232). I believe they are closing them out. If you think you want one, get it now while the price is right!

Chris

 

Chris-
I have an 81 standard duty F250 Ranger Lariat, hence the RL. I now have a 400 in it thanks to TMeyer Inc. I want to be prepared for any road condition, as I am in the Army and could PCS anywhere. I expect to have to haul either across the Rockies or the Appalachia range next. You can check out my build thread for more info (and pictures) as to what I have done so far. As of now, the HB upgrade will most likely be a late fall to winter project.

 

I got the new SD HB unit today so, off we go!

Some comments...

The SD HB unit is a perfect fit to the firewall on this truck. My prior reading of what it takes to put HB on one of these trucks made it clear that either the pivot pin on the brake pedal has to be relocated upwards or the HB has to be moved downwards in order to keep the pushrod angle at something reasonable. In anticipation of this I quickly found (I got real lucky!) the right HB specific pedal for the truck, and it showed up today too! Hot damn, we're off to the races. I had some concerns about the late style HB brake pedal fitting on my '86 Bullnose, but the pedal assembly is identical, as it turns out.

There is a long thread in the OBS forum about the challenges the OP had in getting the required pedal pressure down to something reasonable. He spent two years before getting it figured out. The problem he was having was a hard pedal. The brakes worked well, but the pedal force was substantial.

Keeping this in mind, I looked hard at the pedal-rod relationship while the original pedal was still in my truck. Note, also, that the pivot pin location on my brake pedal was not nearly as out-of-position as it was on his OBS truck, but the side of the rod was still hard pressed against the nose of the HB unit. Pressing the brake pedal would have created even more interference. I don't think it was ever stated specifically in that thread, but the problem was due to major mechanical interference. With the rubber boot on the nose of the HB, this would not be at all obvious.

The point is that you must do something as part of the original HB install, this is not something that can be left until a more convenient time.

So, since you have to do something with the brake pedal, I'll propose a sequence of events to make the install easier. The pedal assembly has six bolts that hold it in place, four of which are the vacuum booster/HB mounting bolts at the firewall. With the MC/vacuum booster removed, two-thirds of the pedal assembly bolts are already out.

The steering column has to come out in order for the pedal assembly to come out though, but this was much easier than I expected it to be. Disconnect the upper end of the steering shaft (the MC and booster are already gone!), disconnect the wiring harnesses, remove the screws at the base of the column going into the firewall, remove two bolts under the dash, and it's out. If you have a clutch pedal, disconnect that MC rod from the pedal assembly.

Though originally obscured by the steering column, the two remaining bolts in the pedal assembly under the dash are now very easy to get to. Wiggle the pedal assembly a little bit, and it's out too.

My pedal assembly includes the clutch pedal and shaft, but just removing the nut on the right end of the shaft is the only obstacle. Pull the clutch shaft out to the left and the brake pedal is free. Very simple and straight-forward.

Once the pedal assembly is re-assembled, put it back in the truck and then slide the HB unit into place to hold that end of the pedal assembly while starting the bolts under the dash. Tighten everything up and then slide the steering column back in. I didn't think of it before removing the column, but the steering lock will keep the steering wheel from turning in the column while it's out.

This is the first time I've ever done this work on a Ford, but the whole thing didn't take an hour. If I had to pull the pedal assembly again, I could probably complete the entire R&R in 15 minutes.

I can't complete the whole project just yet though. I did buy a new SD MC, but the front line fitting is not the same size as on the original MC. I'll have to find an adaptor before I can put a bow on this thing.

When I first started chasing parts, I bought a new SD reservoir for the power steering pump just to make routing of the return lines as nice as possible. The day after ordering it, it occurred to me that I didn't actually know that my existing PS pump was the same as what an SD had. I had done some checking that morning, trying to get some idea what the operating pressure of the stock Ford pump was. Best as I can tell, its normal pressure is in the 700 PSI range. A stock GM pump for use with the HB is 1200 PSI. I don't want to lose any performance here!

Back to RockAuto. I don't know what the difference is, but they do show that the SD pump (no reservior) is a different part number than the stock pump for my truck. Without checking every possible combination, it does seem that the SD pump is SD specific during those years. I was wondering what the difference might be, but it looks exactly the same as the regular pump. Then it occurred to me that Ford almost certainly DID up the pump pressure, specifically because of the HB.

Then I decided that this was all irrelevant. The SD is a big truck designed to handle big loads. That means it WILL have equivalent brakes. I'm done with the debate, just buy an SD PS pump to go with the HB. Done. This was an easy decision for me, as I am also replacing the steering box for a Red Head unit AND the PS fluid looks to be as old as the truck. New HydroBoost, rebuilt steering box, ugly existing fluid. Better to just start with a perfectly clean system.

I've learned my lesson over the years. No more rebuilt pumps for me! When talking to the man at Red Head, I asked if they did pumps too. He said "no", but would strongly encourage getting one somewhere. He said "just DON'T get one of those Cardone units though". Screw it. Turns out that the SD pump was incorporated as standard equipment on all the SD trucks in the 2000s, so it's readily available and not expensive.

Again, sorry for the long post!

Chris

 

Chris - do you have a part number or source for the hydro-boost specific brake pedal that you used?

 

I'm performing this same upgrade on my '86 Bronco. The master cylinder and hydroboost are for 92-97 F350 / F250. I've already upgraded to a saginaw PS pump, so I'll need some custom hoses, but the brake pedal is the part I'm having problems with. Does anyone have a source or even part # for this ?