brake "bomb" (Nitrogen Ball-Pressure Accumulator) replacement instructions

[shogun]

A bad bomb will give you a pedal hard as a rock upon aggressive or panic braking. The pedal will not move and you will need to release and reapply to get normal braking.



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 leas 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: Richard “The Bear” LaBarre

[genphreak]

A bad bomb will give you a pedal hard as a rock upon aggressive or panic braking. The pedal will not move and you will need to release and reapply to get normal braking.

Excellent write-up! It really needs pics as most people have never seen the thing as they are so well squirrelled. Was even so on my old E28, it was the reason I went to a dealer for the fix... I was very impressed at the time, they got to it and some sensor issues fast and cheap (except for the parts cost)... they seemed to think it was affecting the idle if I remember correctly- the brakes were only creeping a bit when holding the car stationery in gear. Nick

[liquidtiger720]

wtf is a brake bomb?

[cmk]

I think they were only on the E31 and E32's

[genphreak]

wtf is a brake bomb?

It was in my braking system on the 535 E28 but I can't remember what for. AFAIK It's not in an E34 535 unless you have self-levelling suspension (LAD) (I think) and is located at the rear for that purpose (ie not braking). I've no idea about the E32.

If it is (I do not have LAD), I've never seen mine... but then again I hadn't on the E28 until they changed it for me, so much so I was incredulous (you know 'wow look at the $$$- the car doesn't even have one!' sort of thought) I went looking afterwards to be sure.... it was beside/under the brake booster and master cylinder assembly. Nick

ps- If the e34 had one I think I would have seen it by now.

[shogun]

Yes, the LAD equipped cars have 2 at the rear. Here you can see how they work and how to replace them
http://shrubbery.student.utwente.nl/...cumulators.htm

[Alexlind123]

My brothers e28 has a brake bomb. When he got the car it needed replacing shortly after, it caused a "lag" upon braking. Like a second or two passed after the pedal was pressed before it started braking. Scary.

[Torque]

Did any e34 at all have this ?

[shogun]

http://www.realoem.com/bmw/partgrp.d...10&hg=33&fg=50
http://www.realoem.com/bmw/showparts...=33&fg=50&hl=1

[cmk]

No.
As mentioned the e34's with LAD have LAD accumulators for the rear suspension.
They did not have the brake pressure accumulator.

The only thing they share is the word accumulator in the name (ok, the brake accumulator may have a nitrogen filled bladder as well, i don't know).
They are for different systems and are not interchangable.

http://www.realoem.com/bmw/showparts...70&hg=34&fg=25