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Thread: Alternative to OEM brake bomb M70

  1. #26
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    It is in the shop manual under integrated suspension system, section 37 21 010 pressure of reservoirs, Druck/pressure [bar]: 23 ,Gewicht/weight [kg]: 1,63

    Regulating control valve: In the level position, the oil bypasses the valve and returns to the reservoir through the return line. A minimum pressure of 440 Psi (30bar) is maintained at all times. If service is required, a bleed off valve is installed on the control valve to drain the systems pressure.
    The problem is, you do not have enough space there for each 2 accumulators on right and left side, including the connections etc. For LAD there is also competition and the prices for new parts are lower, ATE, Meyle, Febi Bilstein make them.
    Last edited by shogun; 03-27-2021 at 09:29 AM.
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  2. #27
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    Here some pics of differences between the Febi brake bomb for the older E32 735, E24, E23, E28 etc against the one used on the E32 750 till around 12/1990 with 1 connection. The adapter parts necessary to use the Febi brake bomb on the 750, also the pipe has to be adjusted by length due to the adapters in between. Maybe someone can find a one adapter piece instead of 2.
    Differences in connections Febi and ATE 750 . Of course one has to fabricate some adapters/brackets for the brake bomb, otherwise it will vibrate too much on the long tube from top of engine bay down behind the foglight. If I change, I will use something like a adjustable pipe bracket. As the imageshack pics of WaaD are no longer working, here a link to Bimmerboard where he posted them http://www.bimmerboard.com/forums/posts/1084178/

    May 2016: I also got the following message from Brunberg in Finland: My 750i is 4/89 so it is with one connection. I have good resource for hydraulic parts etc.
    I got the 735 brake bomb installed, had to kill the OEM pipe but it's now working. Got few photos of that. The project is still going on so I haven't started the car yet, LAD and rear brakes need a lot of work.
    Attached Images Attached Images
    Last edited by shogun; 07-17-2021 at 09:30 AM. Reason: update
    Shogun tricks and tips for the E32 series are HERE!

  3. #28
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    My solution to attach cheap Febi 01817 brake bomb to -89 750i.

    https://onedrive.live.com/redir?resi...hint=folder%2c

    First there is female thread coupler attached to the bomb with loctite 577, then o-ring washer and adapter for hose. At the another end is compression olive for the original tube, sadly you have to cut the original tube. I try to find the parts list, it's somewhere in my garage... Bomb is attached to car with original mounts, drill the spot welds from old bomb(do NOT drill too deep on the bottom part, if the bomb is intact, the high pressure will release). Upper bracket can be mounted under adapter, lower bracket is glued with wurth power tack.

    I have not tested this yet, have to install LAD shocks and rear brakes first. It will work.
    Last edited by shogun; 05-11-2016 at 08:44 AM.

  4. #29
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    Vesa, did you meanwhile test you solution with the Febi brake bomb and the flex hydraulic hose connection?
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  5. #30
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    Yes, I have now tested this solution and it works like new(as I got my brakes and LAD installed)! I had bad pulsating on hydraulic system and all symptoms are now gone, it was so bad it affected also engine idle plus that nasty feeling at brake pedal. Cheap fix, Febi bomb and 20 euros to hydraulic shop.
    Last edited by Brunberg; 09-26-2016 at 07:51 AM.

  6. #31
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    Did someone else make such modification meanwhile to a Febi brake bomb? Any more pics, hints, part numbers for adapters?
    @Brunberg: do you have the total length of your hydraulic hose which you use instead of the pipe from regulator to the new Febi brake bomb?
    Shogun tricks and tips for the E32 series are HERE!

  7. #32
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    Quote Originally Posted by shogun View Post
    Did someone else make such modification meanwhile to a Febi brake bomb? Any more pics, hints, part numbers for adapters?
    @Brunberg: do you have the total length of your hydraulic hose which you use instead of the pipe from regulator to the new Febi brake bomb?
    I had the original pipe with me and made it about same length, the new hose is slightly too long but it still work very well. I had my 750i in use now for about month after the rebuild. Pics on the picture thread.

  8. #33
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    Some cross section drawings of the ATE H31 system, method of operation of the hydraulic brake servo unit
    http://bmw8.us/Brake%20Booster%20Reb...s/image073.jpg
    http://bmw8.us/Brake%20Booster%20Reb...s/image074.jpg
    http://bmw8.us/Brake%20Booster%20Reb...s/image074.jpg
    BMW 8 Series – H31 Power Assist System (copied)
    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.

    Breakdown of the H31 brake booster http://bmw8.us/Brake%20Booster%20Reb...s/image072.jpg

    source http://bmw8.us/Brake%20Booster%20Rebuild.htm
    Shogun tricks and tips for the E32 series are HERE!

  9. #34
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    Needing to replace mine and found out they are NLA. Reading through the thread, I found some great info, but one question. What thread size is required for our pre 1990 750? I saw the photo with the 735i bomb but no info on thread size for the adapters. I am also looking at a bomb from a hydraulic company which I may be able to fill with nitrogen from our aircraft hanger where I work. They use it to fill Oleo struts with it on aircrafts.

    Also it was mentioned that shelf life is approx. 5 years. Is there a date printed on them? I was looking at maybe an ebay purchase if someone has old stock, but afraid of it being older than 5 years.

    BMW 7er Website www.7er.com
    1989 BMW 735i Schwarz (sadly, sold) // 1989 BMW 750iL Cirrusblau Metallic // 1998 BMW 740iL Oxfordgrün Metallic // 2000 M5 Carbon Schwarz ///

  10. #35
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    Did you meanwhile work on that project, Serge?
    Adapters are shown in my post #27

    Pics from WaaD are no longer working on page 1, but he also posted them on Bimmerboard where they are on the forum server there on BB http://www.bimmerboard.com/forums/posts/1084178
    Last edited by shogun; 01-09-2018 at 06:36 AM.
    Shogun tricks and tips for the E32 series are HERE!

  11. #36
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    I have not worked on that project just get Erich but I will be looking into it before I head up to North Carolina for The Vintage meet. I think I may have to go with my plan of ordering a. Accumulator locally and filling jt. I'll post the details as soon as I confirm its operation.

  12. #37
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    Just for info, the brake bomb with 2 connections used from 12/1992 with p/n BMW 34331159749, BMW 34331162056, ATE Nr.: 10.0515-9002.3 is also no longer available.
    34331159749 PRESSURE ACCUMULATOR From: 12/01/1989 To:08/02/1993 (ENDED) Superseded by: 34331162056 (12/01/1992 — ) (latest online dealer sites in Germany say NLA)
    used in
    5er E34 Limousine 530i (HE11/M60), 530i (HE21/M60), 540i (HE51/M60), 540i (HE61/M60)
    5er E34 Touring 530i (HK11/M60), 530i (HK21/M60), 540i (HK31/M60), 540i (HK41/M60)
    7er E32 Limousine 730i (GD11/M60), 730i (GD21/M60), 730iL (GD51/M60), 730iL (GD61/M60), 740i (GD41/M60), 740iL (GD81/M60), 750i (GB81/M70), 750iL
    8er E31 Coupé 840Ci (EF71/M62), 840Ci (EF81/M62), 840i (EF51/M60), 840i (EF61/M60), 850CSi (EG91/S70), 850Ci (EG11/M70), 850Ci (EG21/M70), 850Ci (EG41/M73)
    weight (kg) 1.368
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  13. #38
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    This is most interesting information. This would be one way to save the "bomb" and give it a few more years of service.

    Shogun: Do you have more information about this extra valve or any suggestion to what to use for the extra valve.

  14. #39
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    Quick Connect Couplings, I assume this is a valve for compressed air, gas etc. Basically you need a check valve which can stand that pressure and which fits the couplings of the container connections from which you want to transfer the gas.
    Search for high pressure quick coupling
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  15. #40
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    to refill gas, Citroen owners do that too and there are even services for testing and re-gassing http://www.citroencarclub.org.uk/dru...a26ab55543664d
    https://www.youtube.com/watch?v=l8KaM9bpyu0

    Desmopan diaphragms for LHM spheres for the Citroen, not sure if they fit our spheres, might need to ask. These type of spheres were used on the ID and DS models but also on the Citroen SM, the Maserati Merak and the Citroen CX Break/Wagon rear spheres
    https://citroen-andre.com/new-diaphr...heres/?lang=nl
    http://www.citroenclassics.co.uk/hydraulics.php
    http://www.czasopisma.pan.pl/Content...per.%20pdf.pdf
    https://shop.citroenclassics.co.uk/r...arge-937-p.asp
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  16. #41
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    Dear Shogun,

    I've a 88 750i and my break bomb is dying slowly.
    I've seen Waad posts but I'm not able to find someone selling such bomb to fill.

    What is the reference of the Febi brake bomb to adapt?


    Thanks,

    Mathieu.
    Last edited by shogun; 10-26-2019 at 06:27 AM.

  17. #42
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    Just got a message from our member Samoeuw: Hi Erich, Thanks to your recommandations I finally had replaced the bomb on my car. More than one year later, all is working fine. I just post on a french forum a little report of the work done. The write up is in french but pictures could maybe help other 750 owners. http://www.serie6.com/forum/viewtopi...170418#p170418
    brief google translate of the comments of Samoeuw:
    Hello everyone, I myself own an e32 750il 87 and the issues raised in this discussion interest me because I encounter similar problems on my vehicle, namely, worries of unstable idle. This car has been in the family for more than 20 years, we had to face many problems common to this model, including the problem you encounter Mad-Math with your pressure accumulator. The original part does not exist any more, I like you, looked for an alternative alternative solution. If it helps you, that's how I did it:
    I opted for the fitting of the Febi sphere which is practically the same part except for the hydraulic connection and the absence of fixing lugs.
    On the Febi sphere it is a flat hydraulic connection whereas the sphere of origin is mounted with a conical connection. I cut the cone fitting and welded the flat fitting instead to keep the existing piping (I did not want to put flexible to maintain an original appearance!)
    I retrieved the brackets on the old sphere by drilling at the spot welds. The upper tab can be reused in the state, it is sufficient to insert two flat rubber seals on either side of it to "wedge" below the new hydraulic connection. Regarding the bottom leg, I welded a piece of flat iron to extend it to be able to "pose" the new sphere, all held by an industrial collar.

    I added reinforced tape around the lower leg so as not to "mark" the sphere with the vibrations. The reference BMW of the accumulator is as follows: 34331157210 it fitted the e32 735, M30 engine with H31 hydraulic braking assistance like the 750
    Febi reference number: 01817, it is also found for AUDi reference: 857 612 085 A or 857 612 085
    -----------
    another comment: with the help of a specialist of spheres citroen I will try to reproduce this fitting: http://www.bimmerboard.com/forums/posts/1084178 référence BMW est la suivante: 34331162055, référence ATE, la suivante: ATE 10.0515-0516.3

    special thanks to Samoeuw
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  18. #43
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    Just an update with pic what adapters are needed to convert from original E32 brake bomb with 1 connection to the Febi Bilstein 01817 brake bomb.
    On the Febi sphere it is a flat hydraulic connection whereas the sphere of origin is mounted with a conical connection. Pic is from someone from the German E32 forum.
    Attached Images Attached Images
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  19. #44
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    For reference, if anyone would like to avoid the hassle of creating a brake bomb from parts (although I admire the ingenuity and problem-solving here!!!), I went with this one for $120 https://www.fcpeuro.com/products/bmw...or-34331162054

    I paid someone to install it, as I was unable to loosen the old one.

  20. #45
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    That type fits BMW Brake Pressure Accumulator - ATE 34331162054 533i, 535i, 633CSi, 635CSi, 733i, E32 735i, L6, M5, M6, and many older cars like E28 but NOT the E32 750, that is why we are using the one you linked, but we have to modify the connections.
    This thread is how to replace the no longer available brake booster 34331162055 ,Part 34331162055 was found on the following E32 vehicles: E32, 750i, Sedan, M70, AUTO, EUR, (GB81), E32, 750i, M70, AUTO, EUR, (GB82) ,E32, 750iL M70, AUTO, EUR, (GC81) ,E32 750iL M70, AUTO, EUR, (GC81),750iL M70, EUR, (GC82),, 750iL M70, AUTO, EUR, (GC82). E32, 750iL M70, AUTO, USA, (GC83), 750iLS, Sedan, M70, AUTO, EUR, (GC85)
    34331162055 Pressure accumulator From:12/01/1992 To: 06/21/2013 (ENDED)
    Superseded by:34331159749 (12/01/1989 — 08/02/1993), nonexchangeable retrospectively 34331162056 (12/01/1992 — 04/20/2018), Exchangeable retrospectively
    Supersedes: 34331157335(05/01/1987 — 06/25/1993)
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  21. #46
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    In case someone is planning to do this modification to the Febi 01817 accumulator, please do not forget to make pics and post them here and write in detail how you did it, especially with regards to the adapters and brackets. Pics from Brunberg for download https://onedrive.live.com/?cid=4ab3d...MZJnLB2fGCPDNI
    Shogun tricks and tips for the E32 series are HERE!

  22. #47
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    Looking for longer lifetime for your H31 hydraulic brake bomb and hydraulic seals? A tip from a German shopowner spezialized on E31/E32 cars , when someone asked for long time winter storage tips:

    to protect the pressure accumulator and the hydraulic seals for longer service life: By pressing the brake 20 times when the engine is off, the 100 bar oil pressure is released from the pressure accumulator and all hydraulic components are relieved!
    Shogun tricks and tips for the E32 series are HERE!

  23. #48
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    help with one port bomb

    Quote Originally Posted by shogun View Post
    Looking for longer lifetime for your H31 hydraulic brake bomb and hydraulic seals? A tip from a German shopowner spezialized on E31/E32 cars , when someone asked for long time winter storage tips:

    to protect the pressure accumulator and the hydraulic seals for longer service life: By pressing the brake 20 times when the engine is off, the 100 bar oil pressure is released from the pressure accumulator and all hydraulic components are relieved!
    i stupidly though the e32 used the same bomb as the 850 , i mananged to get a one port 34331162055 unit but have the opostite problem to what you guys have . ie i need a two port bomb and i have paid alot of money for the one port unit

    question

    are the two ports connected ibn parallel to each other ? i ie can i just use a tee connector on my 1 port bomb ?

  24. #49
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    compare on realoem com the 2 versions, hopefully you can find out. If possible, I would install the complete piping from the 1 connection bomb.
    Or sell the one port bomb again and buy the correct one, if still available, I have read that the 2 port bombs are also difficult to get nowadays.
    Last edited by shogun; 03-05-2020 at 05:47 PM.
    Shogun tricks and tips for the E32 series are HERE!

  25. #50
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    Hi Shogun! What kind of febi bomb and adapter did you use? I'm in the same problem, the brake bomb of my 88' 750i is wrong, and I don't know how to solve the problem, I can't find a new one t buy.
    Last edited by shogun; 06-08-2020 at 07:48 AM.

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