Clutch master cylinder and slave cylinder, function check
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2008 Audi S4, 2008 Audi RS 4, 2007 Audi S4, 2007 Audi RS 4, and 2006 Audi S4. However, it is still accessible from the selected car via links, so may be relevant.
Before replacing the master and/or slave cylinder, perform the appropriate checks in the case of the following errors:
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 faulty 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 → Hydraulic clutch system, bleeding .
High pedal force:
- Clutch plate is worn (except for SAC)
- Mechanically defective 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 → Hydraulic clutch 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) defective, replace needle bearing → .
- Foreign material in clutch system
- Mechanically defective pressure plate/clutch plate → Clutch, servicing
- Wrong components used or components forgotten when performing repair work (e.g. intermediate plate).