Clutch adjustment involves setting the correct amount of free play in the release mechanism. Too much free play could cause the clutch to drag (continue to pull or propel car) during clutch disengagement. Too little free play could cause clutch slippage. It is important for you to know how to adjust the three basic types of clutch release mechanisms.
Mechanical clutch linkage is usually adjusted at the push rod going to the clutch throw-out lever (which is also known as the release fork or release lever). See Fig. 17-1. One end of the throw-out lever push rod is threaded. The effective length of the rod can be INCREASED to raise the clutch pedal (decrease free travel). It can also be SHORTENED to lower the clutch pedal (increase free travel).
To change the clutch adjustment, loosen the push rod nuts. You may need to grasp the unthreaded portion of the push rod with vice grips to free them. Turn the nuts on the threaded push rod until you have the correct pedal free travel.
Note! Specific procedures and free travel specifications vary. Always refer to a service manual for exact details.
Figure 6 Fig. 17-1. Mechanical clutch linkage is usually adjusted at the push rod going to the clutch throw-out lever. (Typical)
As with the linkage release mechanism, a clutch cable may require periodic adjustment to maintain the correct pedal height and free travel. Look at Fig. 17-2. Typically, the clutch cable housing will have an adjusting nut. When the nut is turned, the length of the cable housing increases or decreases.
In most cases, to INCREASE clutch pedal free travel, turn the cable-housing nut to shorten the housing. To DECREASE clutch pedal free travel, lengthen the clutch cable housing. Some cable release mechanisms have an automatic adjusting mechanism. If the clutch requires adjustment, the automatic clutch adjuster may be faulty or the clutch may be badly worn.
Figure 7 Fig. 17-2. Clutch pedal free play is distance pedal moves until throw-out bearing touches pressure plate. Release lever or arm free play is distance end of arm moves back and forth with clutch released. Note adjuster nut for changing cable free play. (Honda)
A hydraulic clutch release mechanism may need adjustment after prolonged clutch operation. Normal wear of the friction disc, throw-out bearing, and other parts can cause the pedal free travel to increase. The adjustment of a hydraulic type clutch may be located on the throw-out lever push rod or the push rod going to the clutch master cylinder. See Fig. 17-3 and 17-4.
To adjust a hydraulic clutch, simply turn the nut or nuts on the push rod as needed. Generally, lengthening the rod decreases pedal free travel. Shortening the rod increases free travel. Check a service manual for specifications and procedures.
FLUID LEAKAGE usually causes hydraulic type clutch release mechanism problems. The rubber cups inside the master cylinder or slave cylinder can wear and begin to leak. After enough fluid loss, the reservoir can empty and the clutch will not release.
If leakage is indicated, inspect the system closely. Look behind the master cylinder and at the end of the slave cylinder. If leaks are found, replace or repair the components as needed. Refer to Figs. 17-3 and 17-4.
Figure 8 Fig. 17-3 Exploded view of clutch slave cylinder. To rebuild unit, hone cylinder and replace cap and boot. Also note adjustable push rod for setting free play
After reassembly, the hydraulic clutch will require bleeding (removal of air from inside hydraulic system). Air is compressible and will cause the clutch pedal to be very soft and spongy.
CAUTION! Install only the recommended type of fluid in a hydraulic clutch system. Also, oil, kerosene, or grease must NEVER enter the hydraulic system. These substances can swell and deteriorate the rubber cups. Keep your hands clean!