Story of the rebuilt of a BMW E28 535i 5 series
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Brakes repair

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.

"Bomb" or power regulator change
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.
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.
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.

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.


Power steering fluid and filter change.

1. Remove the cover of the power steering reservoir, then with a syringe remove the fluid. (Don't reuse it.)
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.

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.