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The brake system and accumulator is another weak point on some
BMWs. Cars with hydraulic brake boost systems: 533, 535, 635, 733
and 735, have a 100% failure rate of the pressure accumulator also
called the "bomb" because of its shape.
A couple of things can cause brake problems: Old power steering
fluid (ATF fluid) with old filter, bad power steering pump, bad
brake accumulator, power brake regulator, brake booster or ...
Accumulator Failure syndromes: Brake light coming shortly
on during brake application. Pedal is hard when the engine is shut
down.
Power brake regulator Failure syndromes: Brake light stays
on after brake application, brake pedal hard all the time.
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change |
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1. To replace the "bomb" or the power brake
regulator, you have to remove the whole assembly. This is an easy
job.
2. Locate the power flow regulator located at the left rear corner
of the engine. Tape the brake sensor wires together then remove them
and set aside. |
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3. Place rags everywhere under the hoses. Use special
flare wrenches to remove the different hoses connected to the regulator.
I used rags to protect the hoses ends.
Remove the two screws holding the regulator at the top. |
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4. Remove the regulator/Accumulator assembly then fight
with it to remove the "bomb".
The best is to put the regulator in a vise and remove the accumulator.
(Some used double sided tape for more grips). I used a pipe wrench
to hold the regulator while I was removing the "bomb".
5. Change the "bomb" or the regulator... or both. |
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The brake sensors are also known for leaking. You might want to
change them while you are at it.
Installation is reverse of removal EXCEPT for the two metal hoses
located at the right of the regulator (closest to the firewall),
you HAVE TO install them first, starting with the bottom one, before
putting the two bolts holding the regulator.
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Power steering fluid and filter change.
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1. Remove the cover of the power steering reservoir,
then with a syringe remove the fluid. (Don't reuse it.) |
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2. Remove the different elements, and don't forget
where every piece is going. To remove the clips, use a screwdriver
to pry them out. |
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3. Clean the inside with a rag then install the new filter.
4. Installation is reverse of removal. Fill up the reservoir
with fresh ATF fluid.
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