A4 Quattro Wagon L4-2.0L Turbo (BPG) (2005)
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Clutch Slave Cylinder: Service and Repair
Notes on Removing and Installing Master Cylinder and Slave Cylinder
Notes on removing and installing master cylinder and slave cylinder, 02X, 6 Spd. M/T AWD
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Before replacing the master cylinder or slave cylinder on the assumption that it is faulty, first perform a function check.
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If slave cylinder is removed from transmission with hose/line assembly still attached, make sure you do not press clutch pedal. Otherwise, the
piston will be pressed out of the slave cylinder and be destroyed.
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After installing the slave cylinder carefully press the clutch pedal. If an unusually strong point of pressure is felt when depressing the clutch pedal,
do not press it down further. The push rod of the slave cylinder is likely to have been guided past the clutch release lever. The slave cylinder would
then be destroyed once pedal force exceeds approximately 300 N.
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:
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First check the over-center spring / clutch pedal switch for noise.
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If you hear a noise, remove over-center spring and repeat check.
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Replace relevant component.
After releasing clutch pedal it still remains depressed / does not return to its initial position.
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Check whether clutch pedal returns all the way to its initial position, thereby uncovering the vent opening in the master cylinder.
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The ventilation opening must be uncovered, otherwise permanent self-ventilation for the hydraulic clutch system cannot function.
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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.
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Check brake fluid level in brake fluid reservoir.
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Check master and slave cylinder as well as the line/hose assembly including connecting points for external leaks (visual check).
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If leaks are identified replace the leaking component.
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Bleed clutch system.
High pedal force:
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Clutch plate is worn (except for SAC)
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Mechanically faulty pressure plate/clutch plate
Pedal forces:
Conventional clutch:
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Clutch lining when new: approximately 115 N - Clutch lining at wear limit: approximately 160 N
SAC clutch:
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Approximately 140 N higher for complete service life of the clutch
Clutch does not disengage or does not disengage fully:
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Air in hydraulic system: bleed clutch system.
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Clutch plate does not run smoothly on input shaft splines
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Needle bearing in flywheel (centering bearing for input shaft) faulty, replace needle bearing.
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Foreign body in clutch system
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Mechanically faulty pressure plate/clutch plate.
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Wrong components used or components forgotten when carrying out repair work (e.g. intermediate plate).
