Chevrolet Light Duty Truck 1973 Service Manual page 302

5 -3 6 BRAKES
Fig. 6 9 -Checking Circumferential Thickness Variation
zero. As disc is rotated watch each indicator for
proper tolerance. A micrometer could be used
for this check.
MASTER CYLINDER
Always use clean brake fluid t o
CAUTIO N:
clean any master cylinder parts. Never use
mineral-base cleaning solvents such as gaso­
l i n e , kerosene, carbon-tetrachloridem acetone,
paint thinner or units of l i k e nature as these
solvents deteriorate rubber parts, causing them
t o become s o f t and swollen i n an extremely
short ti m e .
Removal
1. Wipe master cylinder and lines clean with a clean
cloth. Place dry cloths below master cylinder areas
to absorb any fluid spillage.
2. Disconnect hydraulic lines at master cylinder. Cover
line ends with clean lint-free material to prevent
foreign matter from entering the system.
3. Disconnect the push rod from the brake pedal.
4. Unbolt and remove the master cylinder from the
dash panel (or power brake booster.)
Installation
1. Assemble the push rod through the push rod
retainer, if it has been disassembled.
2. Push the retainer over the end of the master
cylinder. Assemble new boot over push rod and
press it down over the push rod retainer. Slide new
mounting gasket into position. Secure the master
cylinder to the dash panel with mounting bolts.
See "Caution" on Page 1 of t h i s
CAUTIO N :
s e c t i o n .
3. Connect the push rod clevis to the brake pedal with
pin and retainer.
4. Connect the brake lines to the master cylinder.
See "Caution" on page 1 of t h i s
CAUTIO N:
s e c t i o n .
5. Fill the master cylinder reservoirs to the levels
shown in Figure 31. Bleed the brake system as
outlined in this section.
. If necessary, adjust the brake pedal free play as
6
outlined in this section.
MASTER CYLINDER OVERHAUL (Fig. 70)
Disassembly
1. Remove the small secondary piston stop screw from
the bottom of the front fluid reservoir of the master
cylinder.
When placing the master cylinder
CAUTIO N:
i n a v i s e , do not tighten too t i g h t l y as damage
t o the cylinder could r e s u l t .
2. Place the master cylinder in the vise so that the lock
ring can be removed from the small groove in the
I.D. of the bore. Remove the lock ring and primary
piston assembly. Remove the secondary piston,
secondary piston spring and retainer by blowing air
through the stop screw hole. If air is not available, a
piece of wire may be used. Bend approximately
1/4" of one end of the wire into a right angle.
Hook this end under the edge of the secondary
piston and pull the secondary piston from the bore.
NOTE: The brass tube-fitting insert should
not be removed unless visual inspection
indicates the insert is damaged.
3. To replace a defective insert the following
procedure should be practiced:
a. Place the master cylinder in a vise, so that the
Fig. 7 0 -Master Cylinder- Explode
LIGHT DUTY TRUCK SERVICE MANUAL