Clutch Hydraulic System: Testing and Inspection

Clutch Master Cylinder and Clutch Slave Cylinder, Function Test

Before replacing master or slave cylinder, you must first carry out the corresponding tests in the event of the following problems.

Noises when actuating the clutch:

• First check the over-center spring and the clutch pedal switch for noises.

• If noises are heard, remove the over-center spring and repeat the test.

• Replace affected component.

Clutch pedal remains on floor or does not return to rest position after recoupling (clutch pedal no longer actuated):

• Check whether clutch pedal returns completely to rest position, thus freeing bleeder hole in clutch master cylinder.

• The bleeder hole is integrated into the clutch slave cylinder. It is not visible from the outside.

• The clutch hydraulic system can only bleed itself when the bleeder hole is clear.

• Explain to the customer that they should not rest their foot on the clutch pedal. It can interfere with the self-bleeding function of the clutch system, because the bleeder hole in the clutch slave cylinder can not perform its function.

• The following can inhibit the self-bleeding function in the clutch system: loose footwell trim or floor mats, a blocked clutch pedal switch or drivers who constantly rest their foot on the clutch pedal.

Check the entire hydraulic system for leaks.

• Check the brake fluid level in the brake fluid reservoir.

• Visually inspect the clutch master and slave cylinders as well as hose/line assembly with its connecting points for leaks to outside.

• If you find leaks, you must replace the affected component.

• Bleed the clutch system. Refer to => [ Clutch System, Bleeding ] 02XA Transmission.

High pedal force:

• Clutch plate worn (except SAC clutch)

• Mechanical defect of pressure plate/clutch plate. Refer to => [ Clutch Repair Information ] Procedures

Pedal force:

Conventional clutch:

-Clutch lining, new approximately 115 N

-Clutch lining, at wear limit approximately 160 N

SAC clutch:

- Approximately 140 N over entire life of clutch

Clutch does not disengage or does not disengage completely:

• Air in hydraulic system, bleed clutch system. Refer to => [ Clutch System, Bleeding ] 02XA Transmission or check hydraulic system for external and internal leakage

• Clutch plate is difficult to move on the driveshaft splines (for example: due to rust or dirt)

• Needle bearing in flywheel (centering bearing for input shaft) faulty, replace needle bearing.

• Foreign body in the clutch system

• Mechanical defect of pressure plate/clutch plate. Refer to => [ Clutch Repair Information ] Procedures

• Incorrect components installed or components missing (e.g. intermediate plate) during repair work.