Chevrolet Corvette 1963 Repair & Tune-Up Manual page 284

264 BRAKES
replaced when overhauling the dual master
cylinder. The displacement capability of the
master cylinder is dependent upon the length
of the secondary piston.
Overhaul
1. Remove the unit from the vehicle us
ing the same general procedure as described
for conventional master cylinders.
2. Remove the mounting gasket and boot,
and the main cover; purge the unit of its fluid.
3. Secure the cylinder in a vise and re
move the push rod retainer and the secon
dary piston stop bolt found inside the forward
reservoir.
4. Compress the retaining ring and ex
tract it along with the primary piston assem
bly.
5. Blow compressed air into the piston
stop screw hole to force the secondary piston,
spring, and its retainer from the bore of the
cylinder. An alternate method uses a piece of
wire, hooked on one end, to snag and extract
the secondary piston.
6. Check die brass tube-fitting inserts and
if they are damaged, remove diem. Leave
undamaged inserts in place.
7. If replacement is necessary, diread a
6-32 x % in. self-tapping screw into die in
sert. Hook die head of die screw widi a claw
hammer and pry die insert free.
8. An alternate way to remove die inserts
is to first drill die outlet holes to
diread diem widi a ^4 in.-20 tap. Position a
diick washer over die hole to serve as a spacer
dien diread a % in.-20 x % in. hex head bolt
into die insert and tighten die bolt until the
insert is freed.
9. Use denatured alcohol and com
pressed air to clean die component parts.
Slight rust may be removed widi fine crocus
cloth.
10. Replace die brass tube inserts at this
time by positioning diem in dieir holes and
direading a brake line tube nut into die out
let hole. Turn down die nut until die insert
is seated.
11. Check the piston assemblies for cor
rect identification and when satisfied, posi
tion die replacement secondary seals in die
twin grooves of die secondary piston.
12. The outside seal is correcdy placed
when its lips face die piston's flat end. The
lips of die inner seal face die piston compen
sating holes.
13. Slip die primary seal and its protector
over die secondary seals. The flat side of diis
seal should face die piston's compensating
hole flange.
14. Replace die primary piston assembly
widi die assembled component found in the
overhaul kit.
15. Moisten die cylinder bore and die sec
ondary piston's inner and outer seals widi new
brake fluid. Assemble die secondary piston
spring to its retainer and position them over
die end of die piston widi die retainer inside
die lips of the primary seal.
16. Insert die combined spring and piston
assembly into die cylinder and use a small
wooden dowel or pencil to seat die spring
against die end of die bore.
17. Moisten die primary piston seals widi
new brake fluid and push it, push rod recep
tacle end out, into die cylinder.
18. Keep die piston pushed in and snap
die retaining ring into place.
19. Relax die pressure on die pistons and
allow diem to seek dieir static positions.
20. Replace die secondary piston stop
screw and torque it to 25-40 in. Ibs.
21. Replace the reservoir diaphragm and
cover.
7984 AND LATER
This master cylinder assembly is an alumi-
num and plastic composite with an integral
proportioning valve/warning switch, individ-
ual reservoirs and a conventional front-to-rear
13
/64 in. and
split. Two outlets are provided for the frontal
brakes, fed from the front reservoir and sec-
ondary piston; with one outlet for the rear
brakes, fed by the rear reservoir and primary
piston. The master cylinder is removed by
disconnecting the brake lines and removing
the mounting nuts attaching the assembly to
the power booster. Cap all brake lines during
service procedures to prevent contamination
of the hydraulic system with dirt, grease or
water.
NOTE: Use only D.O.T. 3 or Delco Su-
preme #11 brake fluid in this brake sys-
tem. Do not use silicone brake fluid such as
Delco Supreme #24, Any type of silicone
brake fluid may cause seal damage. Do not
use lubricated compressed air to blow off
brake parts, as damage to rubber compo-
nents could occur.
Overhaul
1. Remove master cylinder reservoir caps,
separate the cap and diaphragm, then discard
die diaphragms. Inspect the caps for cracks