Pontiac Grand Prix Service Manual page 188

STANDARD BRAKES 5-11
applications. Pull back boot to uncover push rod
retainer. The retainer has a small, depressed tab in the
side and may be pried up to release retainer. Tab
serves to hold retainer and push rod on master
cylinder while it is being shipped and it is not
necessary to bend tab down at reassembly. Retainer is
held in place between master cylinder and dash when
master cylinder is bolted in place.
3. Remove small secondary piston stop bolt from
bottom of front fluid reservoir of master cylinder.
4. Place master cylinder in soft jaws of vise. Remove
lock ring from small groove in inside diameter of bore.
Remove primary piston (rear). Remove secondary
(front) piston, piston spring and retainer by applying
air pressure through front piston stop bolt hole. Do not
attempt to disassemble rear piston since complete new
assembly is provided in repair kit.
NOTE: If air is not available, a piece of wire may be
used. Bend one fourth inch of one end of wire into right
angle and hook end under edge of floating piston to
remove.
5. For your convenience, in the event they are needed,
repair kits contain replacement check valves and
springs. Following are the conditions under which the
check valves should be replaced:
a. Whenever fluid in brake system is contaminated.
b. Whenever foreign material or sediment is found
inside reservoir.
c. If vehicle is 5 years old, or has 50,000 miles or more
on it.
d. If hydraulic brake master cylinder was subjected to
excessive heat such as fire due to accident, etc.
NOTE: In most cases, it will not be necessary to install
new check valves unless conditions above exist;
therefore, unless they do exist, it is not recommended
that the check valves be replaced.
If
check valves do
require replacement, careful& follow the service
procedure outlined below.
6. With master cylinder in vise (outlet holes up), drill
out the tube fitting insert with a 13/64" drill and then
tap
the hole, using a 114'' x 20 tap. Place a 1/2" to
3/4" long, 114" x 20 bolt through a thick washer and
then thread the bolt into the insert. Tighten the bolt
against the washer until the insert is removed.
ports to master cylinder bore to insure they are not
restricted.
9. Remove primary seal, primary seal protector and
secondary seals from front piston.
CLEANING
Use alcohol or clean brake fluid to clean all metal
brake parts thoroughly. Immerse parts in cleaning
fluid using a bristle brush to remove foreign matter.
Blow out all passages, orifices and valve holes. Air dry
and place cleaned parts on clean paper or lint free
cloth.
NOTE: Dirt is the major cause of trouble and wear in
service. Be sure to keep parts clean until reassembly.
Rewash at reassembly
if
there is any occasion to doubt
cleaniness.
ASSEMBLE
1. Place master cylinder in vise, with outlet holes up.
Place check valve springs in outlet holes, so they will
seat in depression in bottom of holes. Place new
rubber check valves over springs, being careful not to
displace springs from their stpt.
2. Place new brass tube seat in outlet holes in position
to be pressed into outlet hole. Be sure that it is not
cocked, as this would cause burrs to be turned up when
the tube seat is pressed in. Recommended method of
inserting tube seat is to thread a spare brake line tube
nut into outlet hole and turn nut down until tube seat
bottoms. (Remove tube nut and check outlet hole for
loose bum, which might have been turned up when
the tube seat was pressed down.)
3. Put new secondary seals in the two grooves in the
end of front piston. Seal which is nearest the end of
the piston will have its lips facing toward that end. The
second groove seal should have its lips facing toward
the portion of front piston which contains small
compensating holes (Fig. 5-4).
4. Assemble a new primary seal and protector over end
of front piston with flat side of seal seating against seal
protector and protector against flange of piston which
contains the small compensating holes (Fig. 5-4).
5. All master cylinder overhaul kits contain assembled
primary piston, making it unnecessary to assemble any
primary piston component parts.
7. Remove check valves and springs from cavities
' 6 . Coat bore of master cylinder, primary and second-
beneath tube seats and discard. ary seals on front piston with clean brake fluid. Insert
secondary piston spring retainer into secondary piston
8. Remove master cylinder from vise and inspect bore
spring. Place retainer and spring down over end of
for corrosion, pits and foreigp matter. Make sure outlet
front piston locating retainer inside lips of primary
ports are clean and free of brass cuttings from
cup.
tube-seat removal operation. Inspect fluid reservoirs
for foreign matter. Check bypass and compensating 7. Holding master cylinder with open end of bore