Bmw E34 Brake booster retrofit

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rs6
Posts: 44
Joined: Tue Jan 28, 2020 7:55 pm
Location: Ljubljana, Slovenia

Bmw E34 Brake booster retrofit

Post by rs6 »

I need some help with the E34 brake booster.
I have problems with my brakes on my 1982 635csi. First I replaced all the brake lines, replaced the whole brake booster for a new one and finally the brake pedal came back to the position. However I had a filling that when I was waiting green light on the hill with pressed brake pedal the car moved forward slowly. Then I noticed that I can press the brake pedal more. But at the end there is limit and the car was still rolling forward when the pedal was at the end of the press.
I got an opportunity to purchase front E32 750il 4pot brake calipers. I'm a bit paranoiac and I want to have the best possible brakes and tires even though I don't really need them. But maybe one day this will help me to stop the car in time. So I bought this 750il brake setup and I Installed them on my E24.
The brake pedal is still soft and the car is still moving on the hills with pressed brake pedal.
So I did a research and I understand why this is happening. But sadly my mechanic skills are not that good and without tutorial or instructions I'm not sure if I can pull this of.
First of all I found an E34 brake booster. Does it have to be from and 540 e34 or it can be from any E34 model?
How is with the installation? I can't find any DIY on the web. I read that it is direct fit on the body. But is there something else I need to connect? There should be a Vacuum hose going to where?
I would appreciate any help with this as I would like to sort this problems with my brakes finally :)
Thanks
wattsmonkey
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Location: Cheltenham, U.K.

Re: Bmw E34 Brake booster retrofit

Post by wattsmonkey »

Apologies if I'm misunderstanding the problem, but if your car is still moving with the brake pedal fully depressed then there is something very wrong with your brakes that requires immediate attention! Master cylinder? Is fluid leaking? I see you've changed out the pipes and - therefore - you must have bled the system.

The booster will change the pedal feel, it won't change the efficiency of the brakes.

The 25mm 750i master cylinder is the recommended swap to retain pedal travel with the E31 brakes.

The other likely culprit is the accumulator (the brake bomb) - if that is dead then the brakes feel wooden and can be frightening as they feel like they are not working at all.

Good luck,
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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