BMW E28 clutch hydraulics: leak, soft pedal and bleeding
Why is the E28 clutch pedal soft or the clutch not disengaging?
The cause is usually a leaking master cylinder by the pedal or slave cylinder on the side of the gearbox. The seals wear with age and fluid leaks out, so the clutch does not disengage properly. The clutch uses brake fluid.
How do I repair a leaking clutch master or slave cylinder?
The cylinder can be repaired with a seal kit if the cylinder is cleaned thoroughly and its surface is intact. If the wear does not come off with honing or the seals show corrosion, replace the whole cylinder. The slave cylinder is cheaper to replace than the master cylinder.
How do I bleed the E28 clutch?
Bleeding is done at the slave cylinder bleed screw, not like bleeding the brakes. First pump the pedal until it resists, press it to the floor, open and close the bleed screw, and let the pedal return fully up before the next pump. Repeat about 10 times while watching the fluid level, until no more bubbles come out.