How to replace Clutch master cylinder of BMW M3 318i 323i 325i and 328i
The following instructions outlines detail procedures on how to replace BMW 3 series (including M3 318i 323i 325i and 328i) Clutch Master Cylinder. First disconnect negative (-) cable from battery. Then remove brake fluid reservoir cap. Using a clean syringe, remove brake fluid from reservoir (Note that brake fluid is poisonous, highly corrosive and dangerous to the environment. Wear safety glasses and 
rubber gloves when working with brake fluid). After that disconnect fluid supply hose from master cylinder. Place a pan under hose to catch any excess fluid.
Working in engine compartment, disconnect fluid line fitting from master cylinder. Working in passenger compartment, remove lower instrument panel trim above pedal cluster. Disconnect clutch pedal from clutch master cylinder push rod by removing clevis pin locking clip and slide out clevis pin. Remove master cylinder mounting bolts (see picture).
The installation is reverse from removal. Fill fluid reservoir with clean fluid. Bleed clutchhydraulics as described earlier. Then connect negative cable to battery last.
Tightening torque:
Clutch master cylinder to bulkhead: 22 Nm (17 ft-lb)
Fluid line to master cylinder/slave cylinder: 16 Nm (12 ft-lb)
