Function check for master and slave cylinder

Before replacing the master or slave cylinder - in the case of the following faults - first perform the appropriate checks.

Noises when operating the clutch:

• First check the over-center spring / clutch pedal switch for noise.
• If you hear a noise, remove over-center spring and repeat check.
• Replace relevant component.

After releasing clutch pedal it still remains depressed / does not return to its initial position.

• Check whether clutch pedal returns all the way to its initial position, thereby uncovering the vent opening in the master cylinder.
• The ventilation opening must be uncovered, otherwise permanent self-ventilation for the hydraulic clutch system cannot function.
• The self-ventilation function of the clutch system can be impaired if the footwell trim or foot mats get trapped, if the clutch pedal switch jams or if the driver rests his foot on the clutch pedal for long periods of time.

Check the complete hydraulic system for external or internal leaks.

• Check brake fluid level in brake fluid reservoir.
• Check master and slave cylinder as well as the line/hose assembly including connecting points for external leaks (visual check).
• If leaks are identified replace the leaking component.
• Bleed clutch system → Clutch hydraulic system, bleeding .

High pedal force:

• Clutch plate is worn (except for SAC)
• Mechanically faulty pressure plate/clutch plate → Clutch, servicing 

Pedal forces:

Conventional clutch: - Clutch lining when new: approx. 115 N- Clutch lining at wear limit: approx. 160 N

SAC clutch: - Approx. 140 N higher for complete service life of the clutch

Clutch does not disengage or does not disengage fully:

• Air in hydraulic system: bleed clutch system → Clutch hydraulic system, bleeding  and check hydraulic system for external and internal leaks.
• Clutch plate does not run smoothly on input shaft splines
• Needle bearing in flywheel (centering bearing for input shaft) faulty, replace needle bearing → 13 - ENGINE - CRANKSHAFT, CYLINDER BLOCK .
• Foreign body in clutch system

• Mechanically faulty pressure plate/clutch plate → Clutch, servicing 
• Wrong components used or components forgotten when carrying out repair work (e.g. intermediate plate).