Mercedes-Benz W123 clutch not releasing or judders
The W123 clutch pedal feels slack or stays on the floor and the gear will not engage. What is wrong?
Usually the master cylinder or the slave cylinder is leaking and air has got into the system. The slave cylinder is on the side of the gearbox on the driver's side. If clutch fluid is dripping under the car, the leak is likely there.
How do you bleed the W123 clutch hydraulics and adjust the free play?
The bleed screw is on the side of the gearbox on the driver's side. Bleeding works from below: open the screw and pump fluid from the bottom until no more bubbles come out. Fluid can also be pushed through the brake caliper bleed nipple. The pedal free play is adjusted with the upper mounting bolt of the master cylinder, which is eccentric.
Why does the W123 clutch judder or not release even though the pedal is on the floor?
The cause can be a broken spring plate on the clutch disc: a piece gets between the friction surfaces and causes juddering or prevents the clutch from releasing. In that case the whole clutch kit is replaced: clutch disc, pressure plate and release bearing. The thickness of the release bearing can vary by model year, so make sure you have the right one before fitting.