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Hydroboost Brakes (MASSIVE TECH INFO)

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ChrisKD:

--- Quote from: joe s on February 19, 2010, 08:36:48 AM ---How about an explanation of the plumbing schematic? It has been a while since I have worked on such trucks. I know it is stupid-simple plumbing, but more info is better info.

If somebody can look up the color codes for the accumulators, that would be great. They are the aluminum cans that store reserve power. One is yellow and one is blue if I recall correctly. They have different amounts of reserve capacity. One was also problematic, and I believe dodge even had a recall.

I also seen mention of contamination being the main cause of failure, and a few guys were running 3/8" clear lexan fuel filters on the low pressure return line. Check to make sure your return line is actually that size, or else you could have a nasty failure. For example, I believe older trucks (1st gen) are 3/8, while I believe mine is some odd-ball 11/32.  ::)

It would be cool if the template comes out the right size and is directly printable. {cool}

--- End quote ---

I can give you the Line/Plumbing Routing  ;)

Right Side of Hydroboost/Toward Engine : Inlet from Power Steering Pump
Left Side of Hydroboost/Toward Fenderwell : Outlet to Steering Box
Left Side of Hydroboost (Rubber Hose with a set of Crimped Clamps) : Return Line

"Gold"/"Yellow" Colored Canister/Accumulator is for Disc-Drum Brake setup  ;)

s ǝoɾ:
I found out something cool.

How to test your accumulator
The accumulator should provide 3 hard power assisted full stops with engine off. To check if it has lost it's charge, simply twist the can or check for "endplay". The accumulator should be under so much pressure that it cannot be twisted or wiggled




--- Quote ---If you are dealing with a vehicle that uses a hydroboost braking system found on certain BMW, Jaguar and Audi models, such as 1980-1992 BMW 7-series, 1983-1992 BMW 533 and 535 models, 1982-1989 BMW 6-series, 1988-1989 Jaguar XJ-6, or 1984-1992 Audi 5000, 100 and 200 models, this might interest you.

Consider the following sequence of events: A 1988 BMW 735 is brought in with a set of brake-related complaints. When the car is first started, the brake pedal is high and hard, and the car wants to creep forward in gear unless a really heavy foot is used on the pedal. After driving a block or so, the brakes feel normal and seem to operate fine. While waiting at a traffic light with the car in gear, the pedal suddenly sinks, often with a jerking, stepwise motion. A quick pump on the pedal brings it back to normal height, but it is hard again. Rolling down the street, the brakes feel fine once more, but a quick stab of the pedal to avoid a car pulling into the lane ahead causes a "Brake Pressure" warning light in the instrument cluster to come on briefly. Symptoms of these sorts may come and go with changing driving conditions.

The car owner is not sure when the symptoms began to appear, but he knows that they have suddenly become much worse. Initial inspection of the brake system does not show anything obviously wrong. The fluid is topped up and clear; no leaks are visible, and pads and rotors are all in good condition. A tech who is unfamiliar with this car's braking system may readily come to the conclusion that the master cylinder has worn seals that are allowing internal leakage, causing the pedal to drop. This does nothing to explain the intermittent high and hard pedal, but it seems a good place to start. Unfortunately, if the master cylinder is replaced, the problems that the car was brought in for will remain.

What the technician needs to know is that this car has a brake booster system unlike the one found in most other cars, and that malfunctions of this system may cause all of the symptoms mentioned above. The car has no vacuum booster; instead, it has a power steering pump (or in the case of the Jaguar, a separate engine-driven pump) that also supplies pressure for braking assist. The brakes need to have boost available for emergency situations even when the engine has died while driving, so there needs to be a reservoir to hold pressure. This reservoir is called the brake pressure accumulator.

The accumulator is a hollow, thick-walled steel ball or cylinder with a flexible diaphragm dividing the interior into two chambers. One chamber is completely sealed and pressurized with nitrogen to approximately 1,100 psi. The other has an inlet for power steering fluid that is pumped in until the nitrogen pressure in the accumulator is over 2,000 psi and the fluid fills a large part of the accumulator's interior volume. The accumulator is mounted on a valve block that controls the direction of flow - from the pump into the accumulator and out of the accumulator to the booster. When the brake pedal is pressed, a valve is opened in the booster that admits pressure from the accumulator to the back side of the booster piston, pushing it forward to operate the master cylinder. Due to the high pressures involved, the actual volume flowing from the accumulator to the booster is very small. This means that a good accumulator can store enough reserve pressure for several emergency stops, even with the engine not running.

With a bad accumulator the story is very different. If the accumulator loses its internal pressure, or a part of it, it also loses the reserve capacity for emergency stops. If it loses enough pressure, eventually it will not be able to supply the booster for even one stop without falling below the minimum working pressure. This turns on the warning light and causes a loss of boost, resulting in a hard brake pedal and increased braking effort. When the internal pressure of the accumulator approaches about 525 psi minimum, an alternately hard and soft pedal may be encountered, as the power steering pump will be able to keep the pressure above the minimum until the brakes have been operated for a certain time, then a loss of boost will occur as it falls below the minimum. This is when the stepwise sinking of the pedal mentioned above will be noticed.

Also due to very high pressures, special pressure gauges and hoses are needed to test this system, and most shops don't have them unless a large proportion of their shop volume consists of cars with hydroboost systems.

A simple and accurate test for a failed or failing accumulator can be made without special equipment. If the car is run at idle for a couple of minutes without the brake pedal being pressed, then the engine is shut off, a new accumulator should allow at least 12 pumps of the pedal (and possibly as many as 20) before it comes up high and hard, indicating loss of boost. A high, hard pedal on the first pump, or even after four to five pumps, indicates an accumulator that has failed or is failing and should be replaced.

Replacement of the brake pressure accumulator is a straightforward procedure that involves unscrewing the accumulator from the valve block, or in some cases, replacing the accumulator and valve block as a unit. Before loosening the accumulator or fittings, be sure to pump the brake pedal at least 20 times to bleed off any residual pressure, otherwise you may be wearing power steering fluid while finishing the job. Always be sure to follow the manufacturer's recommendation regarding steering fluid specifications. Top up the fluid in the reservoir only after running the engine. Pump the brake pedal until it is hard to bleed as much fluid as possible back into the reservoir; otherwise it might overflow during emergency braking conditions. No bleeding of the system is necessary.
--- End quote ---

4x4 440:

--- Quote from: joe s on February 19, 2010, 08:36:48 AM ---How about an explanation of the plumbing schematic? It has been a while since I have worked on such trucks. I know it is stupid-simple plumbing, but more info is better info.

If somebody can look up the color codes for the accumulators, that would be great. They are the aluminum cans that store reserve power. One is yellow and one is blue if I recall correctly. They have different amounts of reserve capacity. One was also problematic, and I believe dodge even had a recall.

I also seen mention of contamination being the main cause of failure, and a few guys were running 3/8" clear lexan fuel filters on the low pressure return line. Check to make sure your return line is actually that size, or else you could have a nasty failure. For example, I believe older trucks (1st gen) are 3/8, while I believe mine is some odd-ball 11/32.  ::)

It would be cool if the template comes out the right size and is directly printable. {cool}

--- End quote ---

Mine has the blue acclumator. Mine did have the oddball 11/32" line but I brazed on a 3/8" tube to -06AN fitting. I will be running -06AN return lines from the hydroboost unit and the powersteering box.

4x4 440:

--- Quote from: joe s on February 19, 2010, 08:36:48 AM ---How about an explanation of the plumbing schematic? It has been a while since I have worked on such trucks. I know it is stupid-simple plumbing, but more info is better info.

If somebody can look up the color codes for the accumulators, that would be great. They are the aluminum cans that store reserve power. One is yellow and one is blue if I recall correctly. They have different amounts of reserve capacity. One was also problematic, and I believe dodge even had a recall.

I also seen mention of contamination being the main cause of failure, and a few guys were running 3/8" clear lexan fuel filters on the low pressure return line. Check to make sure your return line is actually that size, or else you could have a nasty failure. For example, I believe older trucks (1st gen) are 3/8, while I believe mine is some odd-ball 11/32.  ::)

It would be cool if the template comes out the right size and is directly printable. {cool}

--- End quote ---

Joe sent you and E-mail about the install with pics. The template is 6 7/16" by 4 3/4"

s ǝoɾ:
Joe you can edit or add anything you want for this reply.

 

My idea for this was gaining more valve cover clearance for my 440 Ramcharger. First thing I did was gather all the parts needed for the install, you may or may not need all the parts that I used. My truck is a factory D code 1978 Ramcharger, 440 engine, with an 8” lift and a 2” body lift. I am running a Dana 60F and a Dana70 rear axle.

 

Parts that I used are as follows:

1980 or later steering box, metric fittings. I used a 1992 box

Complete Hydroboost system, I used a 1997 unit. Need hydroboost unit, pump and all lines

Brake pedal, part number 4294117, you may or may not need this. My truck used the old style brake pedal, bolt on pushrod. The hydroboost uses the newer style clip on pushrod.

The pedal for a '92 W250 with an automatic is Mopar part number 4294117.  That number seems to also fit all 3/4 ton and 1 ton models with the automatic transmission.  It's a bit strange because the catalog lists one number for D1,4,5 models and then the 4294117 number for D2,3,6 models, which obviously leaves out D7 & D8 models.  Earlier listings show the 4294117 only being used on D350 and W350 models so you can figure it is probably only used on models with 1 ton brakes.  Still, it's an odd listing, even for Mopar.  The 4294117 was used as far back as 1984 and as late as 1993.  So 4294117 is your number and will most likely be found in 1 ton models and some 3/4 ton models from '84-'93.

 

 

 

Install:

Since I have an 8” lift on my truck I am going with crossover steering on my Dana 60F axle. I had to remove the stock steering box and install the new metric box in the 2 wheel drive location. When I did this I had to shorten my Flaming River steering shaft about 5”. I also installed a factory steering box brace to help support the box. These are available in junkyards or from www.dodgeconnection.com If you have a 1980 or later truck and not going with crossover steering you will not need to remove/replace your current steering box.

 

Remove your current power steering pump and lines, pressure and return, from your steering box.

 

Remove the master cylinder and vacuum booster from firewall. I am also installing new hardlines to replace the stock 32 year old ones, you may choose to do this or not depending on the shape if your current lines. Remember to cap the fitting on the intake manifold where your old booster vacuum hose was installed. (no longer needed)

 

Install your hydroboost/power steering pump with hydroboost reservoir in place of where your old pump was installed. You also need the stock pulley installed on the pump. Diesel pumps do not use pulleys. They use a keyed sleeve to drive the pump. This sleeve needs to be pulled off to install the belt driven pulley. (a machine shop can do this or do what I did and cut 2 slots 180º apart and remove the 2 halves) Make sure not to damage the shaft. If you are installing this system on 1980 or later Dodge trucks you have the correct metric pump and may choose to just replace the reservoir with the hydroboost reservoir, has 2 return line nipples.

 

Install the hydroboost unit. I made a template out of sheet metal for two reasons. First was for drilling the two new holes for the hydroboost unit. Second was for making an aluminum backing plate for additional support. I made mine from diamond plate aluminum. I made mine by having a helper holding the sheet metal against the firewall and I marked the stock 4 holes for the booster mounting and the large hole for the push rod. Line up the 2 inner holes, closest to the engine, and the large push rod hole on the hydroboost unit. Mark the location on the sheet metal template for the outer 2 holes of the hydroboost unit. Drill holes in the template. Test fit the sheet metal template on the hydroboost unit. Enlarge holes if necessary. Older trucks like mine use standard size studs. Metric have slightly larger studs. Align template on firewall using the large pushrod hole and the 4 factory holes. Mark and drill 2 new holes for the hydroboost mounting studs. Test fit the hydroboost unit, enlarge holes if necessary.

 

You may choose to use a support plate or not. I used the sheet metal template and transferred it to 1/8” aluminum diamond plate. Drilled all holes, ground down raised surface of diamond plate so the hydroboost unit would be flush with surface of plate, painted it with high temp clear paint, and installed a rubber backing to the back of plate for a seal.

 

Bolt hydroboost unit to firewall, with or without support plate. If using support plate install 2 bolts, washers and nuts in the 2 outer factory holes.

 

Connect all lines. Right Side of Hydroboost/Toward Engine : Inlet from Power Steering Pump
Left Side of Hydroboost/Toward Fenderwell : Outlet to Steering Box
Left Side of Hydroboost (Rubber Hose with a set of Crimped Clamps) : Return Line

 

The line from the unit to the steering box will have to be modified, Newer Dodge trucks have the box mounted to the inner framerail. I just had the loops cut off so it is straight from the hose to the box and had a hydraulic shop re flare it. The high pressure line from the pump to the hydroboost may need a little tweeking to make it work/fit properly.

 

Since I am installing all new hardlines that is as far as I got so far. I also removed the sending unit from the factory proportioning valve and installed it on the hydroboost valve so my factory connector would plug in without splicing. I also removed the RAL unit from the hydroboost unit to make a cleaner install. I also plugged the rear vent fitting on my Dana 70 and removed the tone ring sensor in the axle and fabbed a vent to that sensor plate, for a higher and cleaner look.

 

Any questions you can PM me on the board or E-mail me daltana@ptd.net use the subject line as “hydroboost questions” so I do not delete it.

 

Chris.
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