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Thread: Alternative to OEM brake bomb M70

  1. #1
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    Alternative to OEM brake bomb M70

    Hello All,

    I recently ordered half litre pressure accumulator in local hydraulic shop. They called me last friday to inform me that accumulator is here and to ask me how much nitrogen pressure i need for my application. I Have searched and couldn't find anywhere how much pressure of nitrogen original ATE brake accumulator holds. Does anyone have that info?

    Every information appreciated

    THANKS IN ADVANCE!!!
    Bmw e32 750i 89'

  2. #2
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    11/88 E32 750iL+98 E36M3
    FEBI also makes them, but only for 735 etc. This is the one for E32 735, E28 with 1 connection as used on the older E32 750, but for the 750 the connection is different, no direct fit.
    BMW 34331162054, BMW 34331157210, AUDI 857 612 085 A ,AUDI 857 612 085, FEBI Nr. Art.Nr.: 01817 used in:
    E28: 525i (4131/M30), 525i (4141/M30), 528i (4171/M30), 528i (4181/M30), 535i (DC11/M30), 535i (DC21/M30), 535i (DC31/M30), 535i (DC41/M30), M5 (DC91/S38), M535i (DC51/M30), M535i (DC61/M30), M535i (DC71/M30), M535i (DC81/M30)
    E24: 628CSi (5131/M30), 628CSi (5141/M30), 628CSi (5171/M30), 628CSi (5181/M30), 635CSi (5331/M30), 635CSi (5341/M30), 635CSi (5351/M30), 635CSi (5361/M30), 635CSi (5371/M30), 635CSi (5381/M30), M635CSi (5511/S38), M635CSi (5531/S38)
    E23:728 (6411/M30), 728 (6421/M30), 728 (6501/M30), 728 (6503/M30), 728 (6511/M30), 728 (6521/M30), 728i (6531/M30), 728i (6541/M30), 728i (6571/M30), 728i (6581/M30), 728iS (6431/M30), 728iS (6441/M30), 728iS (6471/M30), 728iS (6481/M30), 730 (6403/M30), 730 (6611/M30), 730 (6621/M30), 732i (6631/M30), 732i (6641/M30), 732i (6671/M30), 732i (6681/M30), 733i (6731/M30), 733i (6741/M30), 733i (6745/M30), 735i (6721/M30), 735i (6781/M30), 735i (6831/M30), 735i (6841/M30), 735i (6851/M30), 735i (6861/M30), 735i (6871/M30), 735i (6881/M30), 745i (6931/M30), 745i (6941/M30), 745i (6961/M30), 745i (6981/M30), 745i (6991/M30)
    E32: 730i (GA31/M30), 730i (GA41/M30), 730i (GA71/M30), 730i (GA81/M30), 730iL (11/M30), 730iL (21/M30), 735i (GB31/M30), 735i (GB41/M30), 735i (GB51/M30), 735i (GB61/M30), 735iL (31/M30), 735iL (41/M30), 735iL (51/M30), 735iL (61/M30)

    FEBI BILSTEIN, 01817 , Details : Inhalt [Liter]: 0,48 , Schaltpunkte [bar]: 100, Gewicht [kg]: 1,14

    for 750 M70 is only made by ATE, ATE 10.0515-0516.3 , but on the ATE site I found these numbers: 340026 10.0515-9002.3 hydr. accumulator ATE, BMW 34331162055 used up to prod. date 12/90, Old part number 34331157335

    from the German forum: es gibt:
    1.) Druckspeicher für die Niveauregulierung = 37211132043, zwei Anschlüsse; 30bar; E24, E30, E34, E32; beschaffbar, BMW, Febi, ATE, Meyle;
    2.) Druckspeicher für die H31 beim 730/735 (natuerlich auch nur wenn die H31 verbaut wurde), = 34331162054, ein Anschluß; 100bar; E28, E23, E24; beschaffbar, BMW, Febi, ATE 10.0515-0515.3 ; SWAG, Textar, FTE
    3.) Druckspeicher für den 750 bis 12/1990 = 34331162055, ein Anschluss; 100bar; NUR beim 750 bis Bj. Dez/1990; bei BMW ausgelaufen, ATE - keine Nachfertigung
    4.) Druckspeicher für den 750 ab 12/1990 = 34331162056, zwei Anschlüsse; 100bar; Verwendung bei M60 Linkslenker, M70 und einige E34 und E31;
    Last edited by shogun; 08-29-2021 at 09:41 AM. Reason: update
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    I have found on many hydraulic sites that nitrogen precharge must not exceed 90% of minimum system pressure for long relyable exploatation. On Shogun's post about H31 http://forums.bimmerforums.com/forum...t-1709393.html is stated that system working pressure is between 35 - 57 Bar, so i decided to charge hydraulic accumulator to 30 Bar. Hopefully this will be much cheaper alternative to oem ATE part.

    Shogun thank you for your effort!

    comment by shogun: added pics from BB, as the ones here are no longer working http://www.bimmerboard.com/forums/posts/1084178/
    Last edited by shogun; 06-06-2019 at 09:55 PM. Reason: added pics from BB, the ones here are no longer working
    Bmw e32 750i 89'

  4. #4
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    How would one know if the bomb need replacing?

    EDIT: The bomb is only on the pre-3/88 cars? With the hydrolic booster? Or is it with the vacuum one as well?
    Last edited by Gold3nMAn; 03-27-2012 at 08:53 AM.

  5. #5
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    11/88 E32 750iL+98 E36M3
    all E32 with a H31 hydraulic brake booster have a bomb.
    That means all 750 over all productions years, plus 735 till or pre-3/88 with hydraulic brake booster isntead of vacuum.

    brake bomb replacement DIY

    BRAKE BOMB REPLACEMENT

    1. Get in car and with engine off, pump brake pedal twenty times (relieves the pressure).

    2. Loosen lug nuts on drivers side wheel. Open hood, and take lid off of PS reservoir.

    3. Jack up and support (jack stands are good) the front end, or a least the driver’s side.

    4. Remove the wheel/tire assembly.

    5. Remove the two bolts in left front wheel housing that hold the alternator intake air duct and remove the duct (this is a horizontal panel of fiberglass and is just below the bomb).

    6. Now you can see the bomb and the two (10 MM or 12 MM) bolts (top and bottom) that support the
    Bomb. You can also see the compression nut, but can’t get a wrench (19 MM on mine) on it.

    7. OK, here is my non professional method of removal:

    a. Using a dremel or any cutting tool, cut a window in the splash panel in front of the tire you removed in the area that will expose the compression nut on the bomb.
    a. Using your open end wrench unscrew (at least break free) the compression nut and then you can hand loosen and remove. Paper towels or rags beneath the bomb will catch any residual fluid that may leak out, do not expect a lot of fluid.
    b. Now remove the two support bolts and the bomb drops out.

    8. Make sure you have a rubber “O” ring gasket to go over the threaded portion of the bomb (my
    Bomb did not come with one and my old bomb had none (dealer item and about $3.00).

    9. Lubricate “O” ring with Pentosin, place over threaded neck of bomb, place bomb in position and lightly (finger tighten) the two support bolts (just to hold bomb in place).

    10. Thread, carefully the compression nut onto the bomb and tighten (it takes only about 30 lb/ft of torque).

    11. Tighten support bolts, top off PS accumulator, start engine, pump up brakes and check PS accumulator one more time, checks for leaks (you shouldn’t have any). Replace panels, replace
    Wheel and tire assembly, lower vehicle to ground, test drive.

    13. Check PS accumulator one more time, and top off if necessary.

    14. I cut a piece of black plastic slightly larger than the window I cut out and RTV’d it over the hole I cut so I am ready for the next time. I bought my BRAKE ACCUMULATOR from Bimmerparts.com, but check for prices, (bombs for735’s are less expensive than 750’s).

    Written by: "Bubba" Richard “The Bear” LaBarre
    ------------------------------------------------
    On the German forum I have read that the bomb can be removed from below when you have the car on a lift or at least on jacks.Dansker who has a repair shop says it can be done in 1 hour:

    Den Druckspeicher kannst Du ausbauen,ohne die Stosstange abzunehmen. Oben am Dom die Verschraubung abschrauben,dann die beiden Halteschrauben am Speicher abnehmen. Eventuell musst Du auch oben am Verteilerstueck die andere Rohrleitung abnehmen,weil Du sonst das Rohr zum Speicher nicht aus dem Verteilerstueck bekommst.Ist Oben etwas Hakelig,das Rohr am Relaiskasten vorbei zu bekommen. Allerdings musst Du etwas mehr Bodenfreiheit haben,um die Bombe mit dem Rohrnach Unten Heraus zu ziehen.(Wagenheber unter die Vorderachse).
    Ich habe das vor circa 2 Monaten so gemacht,(circa 1 Stunde Arbeit)
    Gruss Dansker

    use google translate for this.


    This month I want to discuss a somewhat vintage BMW power brake system, the H31 “Hydro Boost” power brakes and steering system. BMW has always been a leader in technology and never was this more evident then when they introduced the H31 system in the E23 seven series cars in 1977. As is still typical the technology that was debut on the flagship Seven series became a proven design and used on various Five, Six and Seven series cars ending on the Eight series before being phased out with the last of the Eight Fifties in the mid nineties. Over the years I have received a great deal of calls and e-mails regarding the diagnosis and repair of this system. I will attempt to clarify some of the misconceptions and advise on accurate, straightforward diagnosis.

    Unlike almost every other power assist braking system that uses engine vacuum to create the boost, the H31 system used hydraulic pressure from a special power steering pump to create the assist needed. This system allowed for more available assist that was highly controllable in a smaller package then any vacuum boost system available at that time. Soon after its introduction, BMW coupled its race proven BOSCH ABS technology to offer a braking system that became the performance standard that other manufactures where judged by.

    Over the years the H31 system has caused a number of headaches for techs who where attempting to diagnosis this very sophisticated hydraulic system. Most of these headaches are due to a lack of understanding of the basic principles of operation. The original repair information involved the use of very high pressure gauges to test the pump output and the pressure controlled flow regulator known as the DS Regulator with it’s attached accumulator better known as “the Bomb” because of it’s cannonball shape. I have found the use of these gauges to be unnecessary in all but a few rare cases.

    The most common failure of this system is the accumulator (the bomb). It is a round steel chamber with a high-pressure nitrogen filled balloon built inside it. On a normal working system, as the pumps hydraulic pressure builds up it moves fluid into one side of this sphere displacing the balloon and storing pressure and a volume of fluid. Over time the balloon loses its nitrogen charge causing the sphere to lose its spring affect of storing the pressure energy. The simple test of the bomb is to run the car for a minute to allow the pressures to normalize then shut off the engine and then pump the brake pedal until all power assist is lost and the pedal becomes hard. Typically a good accumulator will give you about eight pumps of the brake pedal before you loose assist. A bad one will be hard after one pump and the accumulator needs to be replaced. The second part of the test is to check the DS regulator. Again run the motor briefly to build pressure then shut it off. Now wait five minutes before applying the brakes. You should have at least half the pumps with assist that you had when you did the test the first time. If not the valves in the DS regulator are leaking down to quickly. The DS regulator cannot be serviced and would need to be replaced.

    The common symptoms of a failed accumulator can be an intermittent brake warning light that can come on when the brakes are applied, or a too soft brake pedal that does not improve after bleeding the brake hydraulics. A good check for the brake hydraulics is to pump the pedal till all boost is gone, then if the pedal is still spongy then the problem is in the brakes. Other issues common to the booster system are leaking pressure switches at the DS regulator and leaks at the hydraulic booster. The brake booster leaking will vent power steering fluid (either ATF or Pentosin depending on the system) at a drain hole between the booster and the master cylinder.

    The power steering pump supplying the pressure for this system has a maximum operating pressure of about 130 bar (1900 psi), however the working pressure for the H31 system is regulated at 35 * 57 bar and only needs about ten percent of the fluid volume that is needed for the power steering. With that in mind it is obvious that any problem with the pump pressure or volume would show itself first as a problem in the power steering.

    To properly check the fluid level you must have the engine off, pump the brakes until the assist is gone then remove the cover from the reservoir. The fluid should be at the top of the screen. If not top off with the correct fluid for your car, most early cars used ATF but later BMW’s went to Pentosin fluid, do not mix them and NEVER use brake fluid in the pump hydraulics. Brake fluid will destroy the seals in the H31 system and ATF or Pentosin will destroy the seals in the brake hydraulics. They are separate systems and do not share fluids, IF IN DOUBT ADD NOTHING. If either system is contaminated by the other it can be very expensive to fix and potentially dangerous.

    My last set of problems, are usually listed as power steering complaints. This system uses a very high-pressure, high volume pump; any leaks in the system can be a big mess fast. Many of these cars develop noises in the pump and the pump is replaced only to find that the noise is still there! The problem is from air being pulled into the pump through loose hose connections on the inlet hose between the pump and the reservoir. The leak can be so small it will not lose any fluid but still allow air to be sucked in when the car is running. This problem is exaggerated by the fact that the filter in the reservoir has probably never been serviced and is plugging up with debris. Finally you must consider the condition of the drive belt, a belt failure will immediately cause a loss of power steering and the brakes will only have the stored pressure of the accumulator to assist you for stopping.

    You can only imagine heading to the braking zone at turn three of BIR in your E28 M5 only to find that the belt broke. You would have no power steering and no power brakes if the accumulator were bad. No more M5, Bad day, really, really, bad day.

    Until next time

    Paul Dzimian
    BMW CCA TSA
    Shop Forman
    Motorwerks BMW
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
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    Ok guys, I have just finished retrofit of non Oem bomb in my 750i. Ordered bomb charged with nitrogen to pressure of 30 BAR:
    Oem bomb compared to ordered one:
    Installation of reducer so we can fit new accumulator:
    We removed mount from old bomb. Spot welds are drilled and mount is removed with chisel:
    Mount is welded on nut that will be screwed on gas filling port:
    Finaly bomb is mounted on car:
    Braking is now much better and faster, and feeling is completely different. My gues to charge nitrogen to 30 BAR was right. Now i have around 15-20 pumps before brake pedal becomes stiff.

    http://www.bimmerboard.com/forums/posts/1084178/
    Last edited by shogun; 04-05-2022 at 12:02 AM. Reason: added working pics link
    Bmw e32 750i 89'

  7. #7
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    How much did it cost, compared to original ATE?
    Current rides: E65 730dA '04, F10 520dA '11, E34 520iA '91

    Old rides: E46 316Ti, E53 X5, E38 728iA, E39 528iA, E46 318i Touring, E38 730dA, E36 316i, E36 328iA Cabrio, E38 728i, E38 750i, E36/3 320i, E36 318i, E39 530dA Touring, E38 740i, E39 528iA, E34 525iA, E32 750iL, E32 730iL, E34/2 525TDS,
    E34 525i, E28 518i, E34 535i, E34/2 525iA, E30/5 325i, E34 535i, E28 520i https://www.instagram.com/zener__/

  8. #8
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    Quote Originally Posted by zener View Post
    How much did it cost, compared to original ATE?
    Cost was:

    - Hydraulic accumulator 0.5 l - 75 Euro
    - Reducer 5 Euro

    vs. original which i couldn't find cheaper than 250 Euro and up to 360 euro in some places.

    As far as simptoms of broken bomb is concerned , i have noticed only two, sporadic clicking noise around brake pedall , and very dramatic emergency braking (after pressing pedall you must wait pedall to sink wich takes about half of second to happen).
    Last edited by WaaD; 04-02-2012 at 10:37 AM. Reason: Automerged Doublepost
    Bmw e32 750i 89'

  9. #9
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    found a pic of the bomb with stamped on info 100 bar. That is that is the nominal value for the steel housing with safety margin., not the gas pressure.
    According to the testing instructions :

    Functional test of the hydraulic accumulator
    with the engine switched off, depress the brake pedal about 20 times. The pressure gauge of the test device must rise to 22 + 2 bar immediately after starting the engine. If this value is not reached or exceeded, the hydraulic accumulator must be replaced.
    -------------
    I is said on the German forum that at a pressure below 15 bar the bomb has to be replaced. But the official test instructions say 22 + 2 bar.
    Last edited by shogun; 10-20-2021 at 03:08 AM.
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
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    you are right. I calculated that 30 Bar of nitrogen pressure is going to be enough for aftermarket H31 accumulator. I have it now on my car for some time without any problems.
    Bmw e32 750i 89'

  11. #11
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    Ok, some time has passed and i don't have any problem so far.
    Bmw e32 750i 89'

  12. #12
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    WaaD

    what is the maker of the accumulator you are using now? And the article number?
    Shogun tricks and tips for the E32 series are HERE!

  13. #13
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    Hello Erich,

    Well I don't realy know, I bought generic half liter accumulator, but it seems that it have embossed on side "Olaer" and I can't recognise numbers.
    I checked Olaer Site and found this: http://www.oilsolutions.com.au/olaer...plications.pdf as you can se it can't be different fom 0.5 liter nitroball.
    Last edited by shogun; 04-05-2022 at 12:03 AM.
    Bmw e32 750i 89'

  14. #14
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    partsgeek has the accumulator for 750 cheap up to 12/1990 with one connection , ATE Brake Accumulator Retail Price: $316.63 Your Price: $196.98 Part Number: W0133-1601308. From 12/1990 the part is different + has 2 connections.
    Last edited by shogun; 04-05-2022 at 12:05 AM.
    Shogun tricks and tips for the E32 series are HERE!

  15. #15
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    just to report, no problem so far with my aftermarket brake bomb.
    Shogun thats fair price but i did resolve problem little bit cheaper. Anyway original is always best way to go.
    Bmw e32 750i 89'

  16. #16
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    I just got the info that BMW discontinued the brake booster with ONE connector 34331162055 = 10.0515-05115.1 ATE. Old partnumber 34331157335

    Superseded by: 34331159749 (01.12.1989 — 02.08.1993), nonexchangeable retrospectively, 34331162056 (01.12.1992 — ), Exchangeable retrospectively = the version with 2 connectors, ATE e32 e31 from 12.90, ATE 10.0515-9002.3

    All their stock has been scrapped as storage time was >5 years. ATE does not have the production line anymore for this.
    That is the one used till 12/1990 with ONE connection only, and only used in E32 750.
    http://www.realoem.com/bmw/showparts...34&fg=25&hl=24
    All parts still available in the net are (very) old stock. Normal lifetime for storage is said to be 5 years.

    The other one with one connection was only used on M30 engines
    FEBI,
    BMW 34 33 1 162 054,BMW 34 33 1 157 210, AUDI 857 612 085 A , AUDI 857 612 085 , FEBI Nr. Art.Nr.: 01817 ,Hersteller:

    FEBI BILSTEIN ,Hersteller-ArtikelNr: 01817 : Details Inhalt [Liter]: 0,48 Schaltpunkte [bar]: 100 Gewicht [kg]: 1,14
    BMW 5 (E28) 525 i 110 06/1980 06/1990 ,BMW 5 (E28) 528 i 135 06/1980 06/1990 ,BMW 5 (E28) 535 i, M 535 i 136 06/1980 06/1990,BMW 5 (E28) 535 i, M 535 i 141 06/1980 06/1990, BMW 5 (E28) 535 i, M535 i 160 06/1980 06/1990
    BMW 5 (E28) M5 3.5 211 06/1980 06/1990 ,BMW 6 (E24) 628 CSi 135 04/1976 09/1990,BMW 6 (E24) 635 CSi 136 04/1976 09/1990,BMW 6 (E24) 635 CSi 141 04/1976 09/1990,BMW 6 (E24) 635 CSi 155 04/1976 09/1990
    BMW 6 (E24) 635 CSi 160 04/1976 09/1990,BMW 6 (E24) M 635 CSi 191 04/1976 09/1990,BMW 6 (E24) M 635 CSi 211 04/1976 09/1990,BMW 7 (E23) 728 125 05/1977 08/1986 ,BMW 7 (E23) 728 i 135 05/1977 08/1986
    BMW 7 (E23) 730 135 05/1977 08/1986 ,BMW 7 (E23) 732 i/733 i 145 05/1977 08/1986,BMW 7 (E23) 735 i 136 05/1977 08/1986 ,BMW 7 (E23) 735 i 141 05/1977 08/1986,BMW 7 (E23) 735 i 160 05/1977 08/1986,BMW 7 (E23) 745 i 185 05/1977 08/1986
    BMW 7 (E23) 745 i 185 05/1977 08/1986,BMW 7 (E32) 730 i,iL 138 09/1986 09/1994,BMW 7 (E32) 730 i,iL 145 09/1986 09/1994,BMW 7 (E32) 735 i,iL 155 09/1986 09/1994,BMW 7 (E32) 735 i,iL 162 09/1986 09/1994

    this one does not have the welded on bracket and the connection is different from that of the one for the 750.
    The M30 version has a straight connection and the one for the M70 till 12/1990 has a cone type connection.

    The one for the V8 and the one for the V12 34331162055 and 34331162056 will be no longer available.

    This is the version for the facelift engine with 2 connections http://de.bmwfans.info/parts-catalog...ke_servo_unit/
    A friend in Germany had a look at both versions and his idea is:
    I took a short look at both of them. In my opinion old and new style are interchangeable. Use the pipe/connection of the brake booster # 8 + #9. Close with a blind plug the old connection at the brake pressure regulating valve. See link here
    http://de.bmwfans.info/parts-catalog...ke_servo_unit/
    What I mean is pipe # 1 which goes into the brake pressure regulation valve. This should be plugged with a blind plug and use the new line and brake bomb with 2 connections from the facelift version, that should be possible.
    Important note: as the brake system originally on your car was certified and approved as it is now/original, this modification might cancel your Certificate of Roadworthiness , so all this info is a private opinion and all possible modifications are done at your own risk.

    Best is you contact your local BMW dealer and ask them what BMW is going to do in your country to solve this problem based on local regulations.
    Last edited by shogun; 09-19-2020 at 12:40 AM.
    Shogun tricks and tips for the E32 series are HERE!

  17. #17
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    I just found some good pics of the piping arrangement of the newer version with the 2 connectors http://i-code.net/replacing-bmw-e32-...e-accumulator/

    The older one with 1 connector is no longer available. Some ideas to use the Febi 01817 pressure accumulator also used on the E28, E24, E23, E32 735 1987 model year with H31 hydraulic brake booster. On the E28 the accululator is located in a different location, no pipings in between, so therefore no brackets necessary , p/n 4331162054 http://i18.photobucket.com/albums/b1...W/DSC00734.jpg

    Adapters idea to fit the 750 with that Febi 01817 : needs brackets + connector adapter. Anyway, we have to find a solution for the older 750 like my 11/88 with brake acummulator with 1 connection.
    Last edited by shogun; 04-05-2022 at 12:07 AM.
    Shogun tricks and tips for the E32 series are HERE!

  18. #18
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    Hello, mine was with one connection, and it still work without problem.
    Bmw e32 750i 89'

  19. #19
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    Got some more info/opinions on a non English speaking forum about pressures, working pressure, layout pressures....
    Note: these are private opinions of E32 enthusiasts. Not professionals in hydraulic brake booster systems.

    One comment translated:
    The brake booster operates only at about 50 bar under condition: while the engine is running, and speed independent . The orginal accumulator has not a 100 bar filling , but it is designed for switching points up to 100 bar , in the E32 750 we have set points of 36-58 Bar , so we are not so even near to the layout load limit of the brake booster accummulator. Of course the power steering pump produces more pressure/bar, but the pressure regulator does not allow that more pressure goes thru, it controls it. As a rule of thumb for pressure accumulator: The nitrogen filling must be lower by some bar compared to the lowest pressure on the hydraulic side.

    Another comment translated:
    That's not 100% correct . First, the pressure is 35 to 57 bar . This is the pressure that is " present " at BKV = brake booster . The operating pressure should be at 46 bar + -5 bar . The rule of thumb is based on percent . There are a maximum of 90 % and its not " some bar " . So a maximum of 90 % of the system pressure . At 8 bars are 4 bar less percentage more than 50 bar or even 100 bar. It makes sense technically consistently provide the higher pressures . The energy of 480ml 100bar nitrogen is significantly higher than that at 46bar .
    --------------------------

    Disclaimer: I am not responsible for the correctness, completeness or quality of the information provided and also not for the translations. Liability claims regarding damage caused by the use of any information provided, including any kind of information which is incomplete or incorrect, will therefore be rejected. Working on the brake booster or brake system should be done by professionals. If you make any changes, do it at your own responsibility and risk.
    Last edited by shogun; 10-09-2014 at 09:53 PM.
    Shogun tricks and tips for the E32 series are HERE!

  20. #20
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    1989 BMW 750i M70B50
    My calculation of nitrogen pressure is based on information that minimal system oil pressure is 35 bar. On accumulator manufacturer site is stated that nitrogen pressure shall not exceed 90% of lowest system oil pressure. So I decided that 30 bar should be enough and luckily I was right. Also my H31 is using dexron 3 instead of pentosin since refit without a leak or problem, but also I deleted LAD and cannot recomend dexron in LAD Equiped cars.
    Last edited by WaaD; 11-15-2014 at 06:49 PM.
    Bmw e32 750i 89'

  21. #21
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    2004 330Ci
    Quote Originally Posted by Gold3nMAn View Post
    How would one know if the bomb need replacing?
    You hear an extraordinarily loud BOOM!!! (Joking, of course)
    Last edited by balidawg; 08-16-2018 at 09:50 PM.

  22. #22
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    11/88 E32 750iL+98 E36M3
    Quote Originally Posted by Gold3nMAn View Post
    How would one know if the bomb need replacing? EDIT: The bomb is only on the pre-3/88 cars? With the hydrolic booster? Or is it with the vacuum one as well?
    All E32 750 have the H31 brake booster system, E32 730 M30 and 735 M30 have it only on the pre-3/88 cars.
    By Bryan McPhail : http://blog.fcpeuro.com/2014/05/22/f...oboost-system/
    How BMW’s Hydroboost Braking System Works
    In the 90′s, power brake assist was not vacuum assisted, rather it was provided by a hydraulic system known as the ATE H31 Hydroboost in BMW’s high end cars up to the 850Ci. I’ve read in places that BMW chose this for the V12 powered 850i and 750iL because of the difficulty in fitting the larger vacuum booster into the very cramped engine bay. Certainly those engine bays are tight and hard to work on but I suspect BMW were just as interested in using the performance of this unit in their flagship cars.
    There are 3 main components to this system – the pressure accumulator, the booster and the regulator.
    The accumulator is often known as the “Bomb,” not just because of it’s shape but because of the high pressure it can contain. The bomb is filled with a nitrogen compartment that gets compressed by the hydraulic fluid. This ‘charge’ remains in the bomb even when the system is turned off. The bomb can release a large amount of pressure through the fluid very quickly when required. Fluid from the pump flows to the regulator where it is diverted to both the bomb, and the power steering box (the same pump drives both systems). You can see two electrical connectors on the regulator – these attach to pressure sensors – the top one monitors the pressure coming from the pump, and the side mounted one monitors the much higher pressure at the accumulator bomb. The driver can then be alerted to failure in either of these systems.
    The system still works even if all engine power is lost

    Fluid from the accumulator travels to the input of the booster unit (top right port in picture), there is also a return line to the reservoir (top left port). Simply put, when the brake pedal is pushed in (rod on the right hand side) the hydraulic pressure assists in pushing the output rod (would emerge on left hand side of picture) which acts on the brake master cylinder input rod. One of the performance benefits of the system is that the hydraulic force is constant – it doesn’t vary according to engine conditions like a vacuum system could. A safety benefit is that the system still works even if all engine power is lost – the rule of thumb is that the system should provide 15-20 power brake assists even when the engine is off. Any less and you should suspect failure in the accumulator.On cars 15-20 years old (or younger) the main problem with the system is leaks – the seals inside the booster can give up, leaks can occur at both pressure switches, and the accumulator itself can fail. (a leaking diaphragm allowing nitrogen to leak out and mix with the hydraulic fluid) Luckily all of these parts are still available to buy new.
    -------------------------------
    BMW 8 Series – H31 Power Assist System (also E23, E32 plus.., they forgot to mention this, note by shogun)
    This month I want to discuss a somewhat vintage BMW power brake system, the H31 “Hydro Boost” power brakes and steering system. BMW has always been a leader in technology and never was this more evident then when they introduced the H31 system in the E23 seven series cars in 1977. As is still typical the technology that was debut on the flagship Seven series became a proven design and used on various Five, Six and Seven series cars ending on the Eight series before being phased out with the last of the Eight Fifties in the mid nineties. Over the years I have received a great deal of calls and e-mails regarding the diagnosis and repair of this system. I will attempt to clarify some of the misconceptions and advise on accurate, straightforward diagnosis. Unlike almost every other power assist braking system that uses engine vacuum to create the boost, the H31 system used hydraulic pressure from a special power steering pump to create the assist needed. This system allowed for more available assist that was highly controllable in a smaller package then any vacuum boost system available at that time. Soon after its introduction, BMW coupled its race proven BOSCH ABS technology to offer a braking system that became the performance standard that other manufactures where judged by. Over the years the H31 system has caused a number of headaches for techs who where attempting to diagnosis this very sophisticated hydraulic system. Most of these headaches are due to a lack of understanding of the basic principles of operation. The original repair information involved the use of very high pressure gauges to test the pump output and the pressure controlled flow regulator known as the DS Regulator with its attached accumulator better known as “the Bomb” because of its cannonball shape. I have found the use of these gauges to be unnecessary in all but a few rare cases. The most common failure of this system is the accumulator (the bomb). It is a round steel chamber with a high-pressure nitrogen filled balloon built inside it. On a normal working system, as the pumps hydraulic pressure builds up it moves fluid into one side of this sphere displacing the balloon and storing pressure and a volume of fluid. Over time the balloon loses its nitrogen charge causing the sphere to lose its spring affect of storing the pressure energy. The simple test of the bomb is to run the car for a minute to allow the pressures to normalize then shut off the engine and then pump the brake pedal until all power assist is lost and the pedal becomes hard. Typically a good accumulator will give you about eight pumps of the brake pedal before you loose assist. A bad one will be hard after one pump and the accumulator needs to be replaced. The second part of the test is to check the DS regulator. Again run the motor briefly to build pressure then shut it off. Now wait five minutes before applying the brakes. You should have at least half the pumps with assist that you had when you did the test the first time. If not the valves in the DS regulator are leaking down to quickly. The DS regulator cannot be serviced and would need to be replaced. The common symptoms of a failed accumulator can be an intermittent brake warning light that can come on when the brakes are applied, or a too soft brake pedal that does not improve after bleeding the brake hydraulics. A good check for the brake hydraulics is to pump the pedal till all boost is gone, then if the pedal is still spongy then the problem is in the brakes. Other issues common to the booster system are leaking pressure switches at the DS regulator and leaks at the hydraulic booster. The brake booster leaking will vent power steering fluid (either ATF or Pentosin depending on the system) at a drain hole between the booster and the master cylinder. The power steering pump supplying the pressure for this system has a maximum operating pressure of about 130 bar (1900 psi), however the working pressure for the H31 system is regulated at 35 57 bar and only needs about ten percent of the fluid volume that is needed for the power steering. With that in mind it is obvious that any problem with the pump pressure or volume would show itself first as a problem in the power steering. To properly check the fluid level you must have the engine off, pump the brakes until the assist is gone then remove the cover from the reservoir. The fluid should be at the top of the screen. If not top off with the correct fluid for your car, most early cars used ATF but later BMW’s went to Pentosin fluid, do not mix them and NEVER use brake fluid in the pump hydraulics. Brake fluid will destroy the seals in the H31 system and ATF or Pentosin will destroy the seals in the brake hydraulics. They are separate systems and do not share fluids, IF IN DOUBT ADD NOTHING. If either system is contaminated by the other it can be very expensive to fix and potentially dangerous. My last set of problems, are usually listed as power steering complaints. This system uses a very high-pressure, high volume pump; any leaks in the system can be a big mess fast. Many of these cars develop noises in the pump and the pump is replaced only to find that the noise is still there! The problem is from air being pulled into the pump through loose hose connections on the inlet hose between the pump and the reservoir. The leak can be so small it will not lose any fluid but still allow air to be sucked in when the car is running. This problem is exaggerated by the fact that the filter in the reservoir has probably never been serviced and is plugging up with debris. Finally you must consider the condition of the drive belt, a belt failure will immediately cause a loss of power steering and the brakes will only have the stored pressure of the accumulator to assist you for stopping. You can only imagine heading to the braking zone at turn three of BIR in your E28 M5 only to find that the belt broke. You would have no power steering and no power brakes if the accumulator were bad. No more M5, Bad day, really, really, bad day.
    http://www.bmwccae31.com/DOCS/Brake%...t%20System.pdf

    pic/drawing of the booster section http://twrite.org/shogunnew/files/br...rsection01.jpg

    Brake accumulator R&R http://www.bmwccae31.com/DOCS/Brake%...ator%20R&R.pdf

    Brake Booster O-Ring Replacement http://www.bmwccae31.com/DOCS/Brake%...eplacement.pdf
    Last edited by shogun; 11-21-2014 at 08:19 PM.
    Shogun tricks and tips for the E32 series are HERE!

  23. #23
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    Here is a technical file in German language which explain the system of the H31 brake booster and also of the DS-pressure regulator and how to test it, including pressure information
    http://www.bimmerboard.com/members/s..._H31_00000.pdf
    Excerpt with some info by me:
    the only purpose of the H31 brake bomb is just a power assist storage tank for the brake,so to speak: I type is down from a file I have here in German about the H31 brake booster system and DS-regulator:
    Die hydraulische Bremskraftverstaerkung nutzt rationell eine im Fahrzeug bereits vorhandene Energieversorgung aus. Die Hydraulikpumpe fuer die Lenkkraftunterstuetzung versorgt dabei gleichzeitig den hydraulischen Bremskraftverstaerker mit dem erforderlichen Druckoel. Er hat gegenueber den Unterdruck Bremsgeraeten einen wesentlich hoeheren Aussteuerdruck und ist unabhaengig von der Unterdruckversorgung.
    Funktion H31
    Der Druckgesteuerte Stromregler DS-Regler zweigt aus dem Arbeitskreis der hydraulischen Servolenkung (Umlaufsystem) einen geringen Foerderstrom von circa 0.7 Liter pro Minute fuer die hydraulische Bremskraftverstaerkung (Speichersystem) ab und laedt den Hydrospeicher in in einem Ueberdruckbereich von 36 - 57 bar, ohne dabei die Funktion der Servolenkung zu beeintraechtigen. Das unter Druck gespeicherte Hydraulikoel Volumen steht am Bremskraftverstaerker fuer die Erzielung der Unterstuetzngskraft und uebertraegt diese bei Betaetigung auf den angeflanschten serienmaessigen Tandem Hauptzylinder. Bei Ausfall der Lenkungspumpe ist im Hydrospeicher noch eine ausreichende Druckreserve gespeichert um mehrere Bremsungen mit voller Bremskraftunterstuetzung auszufuehren. Nach Aufbrauch dieser Druckreserve ist die weitere Bremsbetaetigung ohne Verstaerkung jedoch mit erheblich hoeherer Fusskraft, in jedem Fall moeglich.
    Wartung: Am Hydrospeicher koennen nach laengerer Laufzeit geringe Gasverluste auftreten, die jedoch keinen Ausfall der Bremse bewirken, sondern nur die Anzahl der aus dem Hydrospeicher zwischen den Schaltpunkten moeglichen Bremsbetaetigungen verringern.
    Allgemeine Funktionspruefung
    Bei abgestelltem Motor Hydrosspeicher durch ca. 20 Betaetigungen des Bremspedals mit einer Vollbremsung entsprechenden Kraftaufwand den Hydrospeicher entleeren.
    Bremspedal geringfuegig belasten, Motor starten, dabei muss sich das Bremspedal spuerbar tiefer senken. Sollte dieser Effekt nicht eintreten, kann die Lenkungspumpe, der DS-Regler, der Hydrospeicher oder der hydraulische Bremskraftverstaerker BKV defekt sein.
    Einzelpruefungen
    Hydrospeicher wie oben entleeren und Warnschalter von DS-Regler abbauen. An den freigewordenen Anschluss des DS-Reglers das Pruefmanometer 32 4 000 (Anzeigebereich 0-160 bar Ueberdruck) anschliessen (beide Sperrventile sind geschlossen).
    Motor starten und Manometer beobachten. Nach Erreichen des oberen Abschaltueberdruckes (52 + 5 bar) Motor abschalten.
    Dichtheitspruefung DS-Regler und Bremsgeraet
    Faellt der Speicherdruck (Manometeranzeige) innerhalb von 5 Minuten um mehr als 5 bar ab, muss die Ruecklaufleitung am DS-Regler geoeffnet werden. Tritt an der Ruecklaufleitung Leckoel aus, ist der DS-Regler undicht und muss erneuert werden.
    Tritt an der Ruecklaufleitung des DS-Reglers kein Leckoel aus und der Speicherdruck faellt trotzdem ab, liegt eine innere Undichtigkeit des Bremsgeraetes vor. Diese tauschen.
    Funktionspruefung Hydrospeicher
    Hydrospeicher wie oben entleeren. Der Manometerzeiger muss nach dem Starten des Motors sofort auf 22 +2 bar ansteigen.Wird dieser Wert nicht erreicht oder ueberschritten, muss nach dem Abstellen des Motors und der Entleerung des Hydrospeichers der Hydrospeicher ausgetauscht werden.
    Funktionspruefung DS-Regler bei laufendem Motor
    Bei der Pruefung (22 + 2 bar) steigt der Druck weiter bis zum Abschaltueberdruck 52 + 5 bar an. Durch Betaetigen des Bremspedals den Speicherdruck (Manometeranzeige) bis zum Einschaltueberdruck von 36 + 5 bar abbauen. Danach schaltet der DS-Regler wieder auf Speicher laden, der Druck steigt wieder bis 52 + 5 bar an. Werden die Pruefwerte nicht erreicht, DS-Regler tauschen.
    ------------------
    google translated
    The hydraulic brake booster makes efficient use of an energy supply that is already available in the vehicle. The hydraulic pump for the power steering simultaneously supplies the hydraulic brake booster with the required pressure oil. Compared to the vacuum brake devices, it has a significantly higher control pressure and is independent of the vacuum supply.
    Function H31
    The pressure-controlled flow regulator DS-regulator branches off from the working group of the hydraulic power steering (circulation system) a low conveying flow of about 0.7 liters per minute for the hydraulic brake booster (storage system) and charges the hydraulic accumulator in an overpressure range of 36 - 57 bar, without the To impair function of the power steering. The hydraulic oil volume stored under pressure is available on the brake booster to achieve the support force and, when actuated, transfers it to the flanged standard tandem master cylinder. If the steering pump fails, a sufficient pressure reserve is still stored in the hydraulic accumulator in order to carry out several braking operations with full brake force assistance. After this pressure reserve has been used up, further brake actuation is possible in any case without reinforcement, but with considerably higher foot force.
    Maintenance: Slight gas losses can occur at the hydraulic accumulator after a long period of operation, but these do not cause the brake to fail, but only reduce the number of brake actuations possible from the hydraulic accumulator between the switching points.
    General functional tests
    With the engine switched off, hydraulic-safe by pressing the brake pedal approx. 20 times with full braking, drain the hydraulic accumulator.
    Apply lightly to the brake pedal, start the engine, the brake pedal must lower noticeably lower. If this effect does not occur, the steering pump, the DS controller, the hydraulic accumulator or the hydr. BKV be defective.
    Individual exams/tests
    Drain the hydraulic accumulator as above and remove the warning switch from the DS controller. Connect the test manometer 32 4 000 (display range 0-160 bar excess pressure) to the connection of the DS controller that has become free (both shut-off valves are closed).
    Start the engine and observe the pressure gauge. After reaching the upper cut-off pressure (52 + 5 bar) switch off the motor.
    Leak test DS controller and braking device
    If the storage pressure (manometer display) falls by more than 5 bar within 5 minutes, the return line on the DS controller must be opened. If leak oil escapes from the return line, the DS controller is leaking and must be replaced.
    If there is no leakage oil on the return line of the DS controller and the accumulator pressure drops anyway, there is an internal leak in the brake device. Swap these.
    Function test hydraulic accumulator
    Drain the hydraulic accumulator as above. The pressure gauge pointer must immediately rise to 22 +2 bar after starting the engine. If this value is not reached or exceeded, the hydraulic accumulator must be replaced after the engine has been switched off and the hydraulic accumulator has been emptied.
    Function test of the DS controller with the engine running
    During the test (22 + 2 bar) the pressure continues to rise up to the shutdown overpressure of 52 + 5 bar. By depressing the brake pedal, reduce the accumulator pressure (manometer display) up to the switch-on pressure of 36 + 5 bar. Then the DS controller switches back to load storage, the pressure rises again to 52 + 5 bar. If the test values ​​are not achieved, replace the DS controller.
    Last edited by shogun; 09-19-2020 at 01:35 AM.
    Shogun tricks and tips for the E32 series are HERE!

  24. #24
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    1989 BMW 750i M70B50
    True, but belive me you don't want to wait in emergency situation for brake pedal to sink which take about 1-2 seconds if your brake bomb is busted. Steering pump don't have enough capacity to feed brake system in emergency full power braking.
    Bmw e32 750i 89'

  25. #25
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    BMW E32 735i
    I'm wondering - would it be possible to use two of those aftermarket bombs for the LAD?
    What do you think, and what would the proper pressure be?

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