Brake Booster 1971 2800CS Brake Master cylinder and proposition valve

Tony.dreamer

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Hello Folks,
The next step on my restoration is installing the brake system. Questions that I have .
1- as you know the booster on 2800CS is the narrower one. Should I buy a used 3.0 CS or the 2800 CS would do just as good? I have no idea of the condition of the rubber inside even though it appears to hold vacuume but I bet the rubber inside is getting old.
2- how can you test the proportion valve? Is there anywhere(or anyone) that can rebuild the it?
3- I have bought the a set of brake lines from W&N . Any comments or suggestions ?
4- I think it will be best if I order a new master cylinder. Any suggestions ?
By the way, I kept the back brakes as drum brakes ...

Thank you !
 

Honolulu

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Rebuild of the brake proportioning valve has been addressed here before, use the Search function. Not sure parts are available but if you only think to clean it out you should be okay, until/unless it's bought the farm from internal corrosion.

The first E3 I had with the narrow servo had the most wonderful (and strong) brakes of any bimmer I've owned, and that's over two dozen. Unless you know the booster servo to be bad (you suggest it is not) I think you should keep it. After all a "restoration" isn't a true "restoration" unless you keep the original spec parts. As you're keeping the rear drum brakes, what changes occur that indicate you need a new servo?

You bought brake lines? Then install them. You may need to get or make a tubing bender, or find something with appropriate radius around which to bend your lines.

Master cylinder... why change? You don't say.
 

teahead

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Pretty sure the fat booster requires a whole different mounting mechanism. Just rebuild the thin one you got. No real need to change it out for the bigger one.
 

HB Chris

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Each booster has a unique master, just discussed here recently. Doesn't make any difference which one you use (since you are replacing brake lines as position is different) but I vote for originality.
 

Tony.dreamer

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A5E4199E-96A9-448B-AF2A-E9F30DB3BFAE.jpeg 0BEFC1A0-6D98-426A-88FE-3531A2CC2A3D.jpeg Thanks Guys !
I appreciate all your input !!!
I will open up the Master cylinder and rebuild it I guess. The car had been sitting under a tree for over 18 years and tree sap rust proofed part of the car and moisture destroyed some parts. But as I wrote about me falling in love with her as a crazy and /or irrational decision, I decided to resurrect the car.
 

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autowerks

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Hi Tony, your coupe is coming together quite nicely, found a new Master cylinder on Ebay for $150 installed and back on the road again!
 
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