Series One brake master cylinder .

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olympia57
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Series One brake master cylinder .

Post by olympia57 »

Woke the car up after winter hibernation and found the brake reservoir almost empty .
It's weeping out of the rear of the brake master cylinder and has been slowly draining over the six months since last used .
I rebuilt the MC ten years ago and have ordered a couple of rebuild kits from DE and Lithuania ( unavailable locally ) and will refresh it again when they arrive .
However , I would like to fit a new MC but was horrified :shock: at the prices being advertised for one . £600 -£700
The series one MC differs from the later E28 based cars due to the twin servo system used .
Has anyone found an option that would not require difficult and unwelcome pipe mods or even a source for a reasonably priced new item ?
https://www.realoem.com/bmw/enUS/showpa ... Id=34_0200
1981 635 series 1
slfan
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Re: Series One brake master cylinder .

Post by slfan »

Hello,

Do not know if this helps. My very early Series I 633CSI (June 1977) utilizes part number 34311120832. Available at both Autohausaz and Pelicanoarts from OEM supplier ATE for US$ 242-256, respectively.

https://www.realoem.com/bmw/enUS/showpa ... Id=34_0203

Good luck!
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tschultz
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Re: Series One brake master cylinder .

Post by tschultz »

slfan wrote: Sun Mar 31, 2024 1:16 am Hello,

Do not know if this helps. My very early Series I 633CSI (June 1977) utilizes part number 34311120832. Available at both Autohausaz and Pelicanoarts from OEM supplier ATE for US$ 242-256, respectively.

https://www.realoem.com/bmw/enUS/showpa ... Id=34_0203

Good luck!
This is correct for lhd car... rhd with dual system is different from my understanding.
http://www.Drive4Corners.com
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'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
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olympia57
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Re: Series One brake master cylinder .

Post by olympia57 »

Apologies for the delay in responding .
sifan . That's a LHD 23.8 MC whereas mine is a 22.2 RHD item . Apart from the diameter the ports are in a different orientation.

I've removed the MC inspected it and it seems to be score or pitting free . Problem /failure seems to have been surface rust on the outside of the cylinder where the piston stops that has caused the initial seal to pass .
It took me a little time to find a seal repair kit for the 22.2 bore but I've sourced three ( NL,DE and Latvia ) and will keep the two spares in stock .
I'll rebuild and refit this week and if all goes well then OK if not then I'll opt for an exchange recon unit from UK .

Then just got to bleed it .........and those that have had that pleasure on a series one will know :cry:
1981 635 series 1
slfan
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Re: Series One brake master cylinder .

Post by slfan »

Olympia57,

Glad that you sourced some seal repair kits. Good luck with the repair.

Regards,
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