'83 733I/A Brakes

[Gympie]

New owner and my first BMW. Understand a service manual is impossible to find for the subject automoile. So will have to rely on you (all's) expert opinions.

My brakes are on the soft side. When stepping on the pedal it is initally hard, then sinks a little, but not to the floor. Just does not seem very solid. Get no warning lights. I understand by a web search a Brake Accumulator is used on a BMW in which the PS pump is used as a secondary for the brakes. Could this be the problem?

If so, where is the accumulator, and how is it replaced? Looks like all the World Pac clones have them in stock.

Gympie

[bigsix]

Yes, you need an accumulator(BRAKE BOMB),they run in the $60.00 range.It is located on the drivers side fender well .If you need a manual it is available on CD-ROM or get a Haynes manual for the 3 and 5 series as the 533i,535i/is, 733i and 735i all have the same accumulator.If you need any help please feel free to email me .


Mark

[email protected]

[Gympie]

Thanks for your reply.

Have found the accumulator and have spent some midnight hours researching on how to replace it. But did run across a disturbing posting in a Roundel article. It stated the accumulator goes south only when the brake regulator is defective. Now this is a pricey piece of hardware to say the least! The article further states that if replacing the accumulator alone will damage the PS pump, regulator, and rack. Now this gives me a real scare to say the least. Any truth to this?

Thanks for the lead for a service manual. Would like to purchase it on CD. Talked to my local BMW parts manager about it and he acted as if I wanted to buy a atomic bomb manual from him.

Gympie

[Arch Angel]

You could have a bubble in the system that might be why your foot goes almost all the way to the ground you can try it

[bigsix]

The Roundel article is incorect. I have replaced several bad accumulators without replacing the regulator. Regulators rarely need to be replaced . You will not damage the other parts if you just replace the brake bomb.

[jeff '84 733i]

The symptoms you have described do not sound like a bad accumulator to me. It sound as though you need to check the level of ATF in the hydro booster and bleed the brakes. A bad brake bomb (accumulator) will give you a sloppy pedal and then if you pump it the pedal will get rock hard until you can't modulate the brakes at all.

First try this. Before you start the car, take the top off of the hydro brake booster which is that large gold cylinder with a thumb screw on a USA car's driver's side of the engine compartment. There is ATF in there. Note the level of the ATF. Pump the brake pedal 15 times and then go check the level of the ATF. If the ATF level is not 1/2" from the top then you should add some more until the level is correct. This is an important note: DO NOT USE BRAKE FLUID! USE ATF!

The brakes on the e23 have to be bled crossways. I.E. Bleed the left front then the right rear. Then the right front and the left rear. The reason for this is that the brakes are engineered as two separate closed systems. The brake master cylinder is set up so that if any brake system is lost the other will still be available for an emergency stop.

Completing Both of these tasks should firm up your brake pedal. If not, your culprit is most likely your brake master cylinder NOT the accumulator. Good luck and let us know what you find.