Chevrolet 30 Series 1967 Service Manual page 245

spots may be polished out with crocus cloth. Never
use emery cloth or sandpaper. If scratches or cor­
rosion are too deep to be polished out, replace
cylinder.
2. Check fit of new pistons in cylinder bore, using a
feeler gauge (fig. 55). Clearance should be within
0.002" to 0.004". Replace cylinder if clearance
exceeds 0.004".
Assembly
Before assembling wheel cylinder, be sure each part
has been cleaned in denatured alcohol.
CAUTION: Do not use kerosene or gasoline for
cleaning wheel cylinder parts. Dip each internal
part in hydraulic brake fluid before assembling.
D u o - S e r v o T y p e
1. Place pistons, cups and spring or spring assembly
in cylinder with parts positioned as shown in
Figure 53.
2. Assemble boots and push rods, then install boots
over ends of cylinders.
T w i n p l e x T y p e
1. Place pistons, cups, spring and expander assembly
in cylinder.
2. Assemble boots on push rods, being sure bead on
boot engages groove in push rod. Install boots and
push rods on cylinder, engaging bead on outer edges
of cylinder housing.
T y p e "F "
1. Insert piston spring, cup filler, and cup into cylinder
bore. Cup filler bumper and cup lip must face closed
end of cylinder.
2. Assemble boot on piston, making sure the boot snaps
over the brake shoe guide.
3. Install piston and boot, inserting piston into cylinder
and engaging boot lip in groove in edge of cylinder.
Position brake shoe guide so slot in guide is parallel
with flat mounting surface of cylinder.
Fig . 55—C hecking Wheel C ylin d e r Piston Fit
T y p e "F R - 3 "
1. Install pistons, piston cups, and spring, with cup lips
toward inside of cylinder.
2. Assemble push rods and boots, then install on cylin­
der. Seat boots evenly in cylinder grooves.
T y p e
Installation
Duo-Servo
1. Position wheel cylinder on flange plate and attach
with cap screw and lock washers. Refer to torque
specifications at rear of manual for correct torque
values.
2. When brake line connector is used, install connector
with new copper gasket. Install bleeder valve in
upper opening in cylinder housing.
3. At rear, connect metal brake tube to wheel cylinder
or to connector. At front, thread brake hose fitting
into wheel cylinder housing or connector, using a
new copper gasket on hose fitting. Insert fitting at
other end of hose through frame and secure with
toothed lock washer and nut or with spring lock,
depending upon type used. Connect metal brake tube
to hose fitting inside frame side rail.
4. Install brake shoes as directed under "B rak e Shoe
Installation Bleed brake system as previously
. ' '
directed under " Bleeding B rakes."
T w i n p l e x T y p e
NOTE: Upper and lower cylinders are not
interchangeable. Lower cylinder has threaded
inlet opening drilled near center of cylinder
bore. Upper cylinder has threaded bleeder valve
opening drilled at extreme outer edge of cylinder
bore. Cylinders must be positioned with con­
necting tube openings toward each other.
1. Position heat shields on cylinder, place wheel cylin­
ders on flange plate, and attach with cap screws and
lock washers. Tighten cap screws firmly.
2. Install connecting tube between the two cylinders and
tighten connections firmly. Connect brake tube to
inlet opening in lower cylinder at inner side of flange
plate. Install bleeder valve in threaded opening in
upper cylinder at inner side of flange plate.
3. Install brake shoes as directed under "B rake Shoe
Installation." Bleed brake system as previously
directed under "Bleeding Brakes."
T y p e "F "
NOTE: The two wheel cylinders mounted on
each brake are identical; however, cylinders on
right-and left-hand brakes have opposite cylinder
castings. Clean mating surfaces of cylinders
and flange plate to insure proper alignment.
1. Place each cylinder on flange plate and attach with
one large and two small cap screws and lock
washers.
2. Position wheel cylinder connecting tube and fitting
assembly and attach fitting to lower opening in upper
cylinder with inlet connector, using new copper gas­
ket on both sides of fitting. ^Attach fitting to lower
opening in lower cylinder with special bolt, using
new copper gasket on both sides of fitting. Tighten
inlet connector and special bolt firmly.
BRAKES 5-29
CHEVROLET TRUCK SERVICE M ANUAL