3. Once the piston is out, inspect the cylinder for wear
or pitting. If the cylinder bore is worn or pitted, the
cylinder must be replaced. Remove the old seals from
the piston and discard them. Thoroughly clean all
parts and allow them to dry.
Caution: Do not allow any petroleum-based
solvent to remain on the cylinder or piston.
4. Install the return spring, when there is one, in the
cylinder.
5. Obtain new seals. Make sure they are the correct ones.
Lubricate them with brake fluid, never with petroleum-
based lubricants, and install them on the piston.
6. Install the piston in the cylinder. Be careful not to
damage the new seals.
7. Install the retaining snap ring, pushrod, and boot.
8. Install the rebuilt cylinder.
9. Attach the hydraulic line. There should be no air in
hydraulic lines; if there is, it must be removed by
bleeding the lines. If the hydraulic system was dis-
assembled for any type of repairs, you must bleed
the lines to remove the air. Once the bleeding
operation is finished, pressure on the pedal should
apply the clutch firmly. There should be no spongy-
pedal feel.
The slave cylinder has a bleeder valve for bleeding
air from the system. The valve looks like a screw with a
small hole running down its length. The hole is closed
off when the bleeder valve is tightened down. Loosening
the valve a few turns will open the hole and permit sys-
tem bleeding. Note that some bleeder valves have a cap,
as well.
There are two methods to manually bleed air from a
hydraulic system. One method is preferred over the other
because it minimizes the chance of fluid contamination.
This preferred method is outlined as follows:
1. Fill the system reservoir with fresh brake fluid. Leave
the cover off the reservoir. (Bleeder valve is closed.)
2. If the bleeder valve has a cap, remove it at this time.
Attach a hose to the end of the bleeder valve. Place
the free end of the hose in a clear container. Fill the
container with enough fluid to cover the bottom of
the hose.
3. Have an assistant pump several times on the clutch
pedal. Then, ask the assistant to hold the pedal down.
4. Open the bleeder valve by loosening it about a quarter
or half turn. Make sure your assistant continues to
keep his or her foot on the clutch pedal. The pedal
will probably go all the way to the floor. Air, or a mix-
ture of air and brake fluid, will come out of the bleeder
valve. Keep the outlet of the hose submerged in the
fluid as it begins to fill the container. Watch for air
bubbles.
5. Close the bleeder valve once the flow stops.
6. Let up on the clutch pedal.
7. Repeat the process until only brake fluid comes out of
the bleeder valve. This can be noted by watching the
air bubbles emerging from the hose as the system is
bled.
8. Top off the system reservoir with fresh brake fluid, and
put the cover back on the reservoir. Do not reuse fluid
bled from the system, as it may be contaminated.
There is an alternative method of bleeding air from a
hydraulic system. It can be done without an assistant and
without wasting brake fluid; however, expelled fluid,
136 Manual Drive Trains and Axles
Pushrod
Dust boot
Snap ring
Washer
Reservoir
cap
Reservoir
Retaining
clamp
Stem tip
seal
Valve
stem
Retainer
spring
Spring
retainer
Return
spring
Valve stem
retainer Piston
Piston
front seal
Piston
rear seal
A
B
Spring
Bleeder
valve cap
Bleeder
valve
Seal
Piston
Snap ring
Dust cover
(boot)
Pushrod
Master cylinder
Figure 7-14. Study the exploded views of master and slave
cylinders. A—A master cylinder is shown. The shape, the
included parts, and their layout can vary. The manufacturer’s
service manual should be consulted for an exact breakdown of
parts. B—A slave cylinder is shown. It, too, can vary as to parts,
shape, and layout. (DaimlerChrysler, General Motors)