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STOP Important Notice Clutch Master Cylinder Failure 1993 88 GM C and K Pickups The clutch master cylinder housing can fracture or seals can be blown out due to excessive hydraulic pressure build up Fig 1 Fractures in plastic units can begin as a small crack creating a leak which can later develop into a visible crack in the clutch master cylinder housing Also for those units made of sheet metal seals will blow out due to the same high pressure build up This is often mistakenly diagnosed as a defective master cylinder especially after repeated failures The various possible causes for this problem are A binding clutch fork ball stud A restricted line to the slave cylinder An incorrect clutch pressure plate requiring a greater force to be exerted The most common cause of master cylinder fracture has been reported to be a binding clutch fork or throw out lever Fig 2 If the area of contact between the ball stud and the clutch fork is binding from lack of lubrication hydraulic pressure in the clutch system can rise substantially Excessively high pressure can cause the master cylinder to fracture If there is a squeaking in the clutch fork or increased pedal resistance the ball stud and clutch fork should be inspected and lubricated or replaced IMPORTANT Grease should be added SPARINGLY to the grease zerk fitting located on the transmission casing Fig 3 Excessive grease can contaminate the clutch disc friction surfaces resulting in slip or chatter and the need to replace the disc The grease zerk fitting may not be readily visible on high mileage vehicles and may require cleaning away of road dirt to make the fitting visible and serviceable Lubricate grease zerk fitting at 30 000 mile intervals with a hand operated grease gun only DO NOT LUBRICATE MORE OFTEN Finally visually inspect the line from the clutch master cylinder to the slave cylinder for any kinks or other damage which could cause a hydraulic restriction GREASE ZERK FITTING 9900000
