318 is master cylinder.

[D. Clay]

What is a low cost alternative to buying a new $180 master cylinder?
What are the compatible upgrades for a 1991 model? I have heard about a larger capacity master cylinder from a 88-94 750il. Has any done this upgrade?

[M42Iberia]

i've heard of people using the master cylinder from the 735i and some one from an e34 which have larger bores...i have an extra one from a 318is if you need it though...let me know!

[gazellebeigem3]

an e32 (i think) 750 MC will give you better pedal feel. I dont remember how much they are though.