WTB Master cylinder

autowerks

autowerks

Well-Known Member
Site Donor
Messages
561
Reaction score
82
Location
Dallas, Texas
My brake master cylinder gave up the other day, like to buy a REAL good used one, rebuilt or if someone is ordering from W/N I would help with shipping cost. Thanks in advance Joe
 
I just pulled a known good master cylinder off my 1980 633csi which has the same big vacuum unit. Realoem shows that part number 34311120832 is used on both a 3.0cs as well as the series 1 E24. Let me know if it would work for you. I bought this car as a driving car with no mechanical issues and can confirm no leaks and good brakes.
 
Thanks WISE9UY, Mine is a 71 2800cs, does it work for sure?
If it works a couple of pics please, Thanks Joe
 
All replacement brake masters are cocked 45 degrees towards the fender requiring you to bend the metal supply line a bit and you may need to flatten the ridge in the upper right corner of pedal box opening in firewall.
 
Last edited:
No problem WISE9UY,
Chris I am confused, what does a brake master has anything to do with the Pedal box opening? Please explain
 
No problem Chris, Its just that I am already thinking brake master headache, now a 45 degree brake master and pedal box work?
that confused me more than I already was!
 
2800CS is different, owing to the fact that it has rear drums. The rear fluid output is a different size to accommodate the residual pressure valve. That makes it identical to a 2002tii master cyl, as it is the larger 23mm bore size and also has rear drums.

All that said, I have one on hand. It's all in pieces and in good condition internally. I have enough good used seals to put it back together, or it can be done with the new kit from BMW. I'd sell it either as-is, or rebuilt used, or rebuilt new. Your choice.
 
So I finally compared the one I took off a 1980 633csi with that on my 2800cs and they appear the same. @Layne do you mean to say that the rear fluid output connection is larger? I will have to take a closer look then. The number of outputs, position, overall length and attachment appear the same.
 
WISE9UY said:
Layne do you mean to say that the rear fluid output connection is larger? I will have to take a closer look then. The number of outputs, position, overall length and attachment appear the same.
Click to expand...

Yes. On the 3.0cs MC, all ports are 10mm. On the 2800CS/2002tii one, the rear output is 12mm (I think) to accommodate the residual pressure valve. I imagine you could adapt it down to 10mm, but probably not the other way.

IMG_1780[1].JPG
 
Layne said:
Yes. On the 3.0cs MC, all ports are 10mm. On the 2800CS/2002tii one, the rear output is 12mm (I think) to accommodate the residual pressure valve. I imagine you could adapt it down to 10mm, but probably not the other way.
Click to expand...

Thank-you for taking the time to post the comparison. I will get in there and take a closer look with a mirror. It is good to learn these differences :) The one I have is like the one on the right.
 
Interesting. The change in MCs however occurred when the booster went from thin pancake style to the thicker fat booster during the 73 MY at 2240222 and 2250146 for the US and 2262256 for CSi and June 72 for CSLs. The Parts Book does indeed show the 12mm screw/plug on the early Masters only. For fun I checked the e3 MC and it is different from both but has the same bore as 3.0CS at 22.2mm while 2800CS is 23.81mm.
 
you are right Layne, mine looks like the one on the left, but there is only a reduction from 8mm size hole to 6mm line.
Are the internal parts the same and Let me know what you would like to get for yours?
 
You must log in or register to reply here.
Back
Top