Master cylinder remove and install

If possible, drain brake fluid from reservoir with a syringe. If nothing is available, remove the cap and  the clutch master feed hose from the side of the reservoir. Pull the reservoir up and off the master cylinder.
This will cause a mess, but brake fluid will not do immediate damage to anything. It will, however ,damage painted surfaces if left sitting on them for any period of time.  Do not wash down spilt fluid with master cylinder is open. Either plug or cover the master cylinder before washing down spilt brake fluid. Brake fluid is water soluble, and a bucket of water tipped down the inside of the engine bay ensures total removal of spilt fluid. Do not use high pressure water as the protective caps on BMW wiring connectors do not supply protection from high pressure water and corrosion of electrical connectors will result.

Disconnect the brake lines from the master, use an 11mm flare nut wrench, rather than an open end wrench. Flare nut wrenches are specifically designed to open line fittings without damaging them.

Remove mounting nuts, 13mm, and slide master cylinder forward and out of the brake booster.

Installation

Ensure rubber seal is located on rear of master cylinder. Failure to install this seal will cause a loss of vacuum assist.

Ensure rod fits correctly in sleeve at rear of master cylinder.

Check and if necessary , replace the rubber grommets that the reservoir fits into.

Bleed system

Tighten brake lines to 14.2 Nm (10ft lbs.)

E30 M3 Repair Manual V2.7.  Copyright ©1999-2001 Koala Motorsport & Brett Anderson