Chevrolet 10 Series 1970 Service Manual page 257

Single Cylinder
1. In stall boot in position and in stall main cylin d er to
fir e w a ll with bolts, w ashers and nuts.
2. Connect hydraulic lin es
c ylin d er.
3. Connect brake pedal return spring.
M A IN CYLINDER ( 4 0 -5 0 -6 0 )
(W ith Frame M ounted Booster) (Fig. 3 2 )
Removal
1. W ipe m a ster cylin d er and lin es clean with a clean
cloth. P la c e dry cloths below m aster cylin d er to
absorb any fluid sp illage.
2. Disconnect hydraulic lin es at m aster cylin d er. C over
line ends with clean, lin t- fr e e m a teria l to preven t
fo re ig n m atter fro m entering system .
3. Disconnect battery ground strap o r stop ligh t w ire s
and brake warning switch w ire.
4. R em ove nuts, bolts, and w ashers which fasten m aster
cylin d er to dash. P u ll m aster cylin d er straight o ff
push rod and rem ove fro m
5. Rem ove and d iscard m aster cylin d er push rod boot.
6. Rem ove m aster cy lin d er c o v e r and pour out fluid
fro m r e s e r v o ir s . Pump the rem aining fluid out by
depressin g piston.
Installation
1. A ssem b le new boot on brake pedal push rod.
2. P la c e m aster cylin d er in position in engine com ­
partm ent. Make certain that push rod and boot a re in
p ro p er position.
3. Fasten m aster cylin d er to dash with nuts, bolts, and
washers.
4. Connect brake lines to m aster cylinder.
5. F ill the r e s e r v o ir s with recom m ended brake fluid to
le v e l shown in S e rvice Manual F ig . 15.
6. F o llo w instructions
B ra k e s ."
7. If n ecessary, adjust the brake pedal freep la y as
d irected .
8. Connect battery ground strap o r stop light w ire s and
brake warning switch w ire (w hichever was discon­
nected at rem o va l).
9. T e s t brakes and make any n ecessary adjustments if
operation is not sa tisfactory.
Disassembly (Fig. 32 )
1. Rem ove cylin d er c o v e r bolt and gasket.
2. L ift o ff r e s e r v o ir c o v e r and c o ver seal. Pour out any
excess fluid and stroke piston to fo rc e fluid through
outlet ports.
3. R em ove piston stop bolt and gasket fro m bottom of
r e s e r v o ir housing.
4. Use snap ring p lie r s and rem ove retain er ring from
gro o ve in end o f cylin d er b ore.
5. R em ove stop plate.
6. A ll internal parts should slide e a s ily out of cylin der
b ore. If they do not, apply com pressed a ir ca refu lly
at fron t outlet port. If parts do not rem ove ea sily,
exam ine b ore c a re fu lly fo r extensive damage which
may elim inate the p o s s ib ility o f reconditioning the
m aster cylin der.
Cleaning and Inspection
Clean a ll parts in denatured alcohol o r brake fluid. If
r e s e r v o ir housing is d egreased, finish clean to rem ove
at dash, toe pan,
engine com partm ent.
under heading of " Bleeding
a ll trace of other solvents.
scratches o r corrosion . M inor blem ishes can be rem oved
with crocus cloth o r a clean-up hone.
and Check by-pass ports in both r e s e r v o ir s to make sure
they are open and fr e e of bu rrs.
R em ove and discard a ll rubber parts. A ll rubber parts
a re included in re p a ir kit which is available fro m regu lar
s e r v ic e parts sources.
Assembly
1. Coat a ll parts with a lib e ra l amount o f brake fluid.
2. Install rubber seal cup on secondary piston with cup
lip facing re a r (open end o f c y lin d er).
NOTE: A ll other cup lips face opposite d ir e c ­
tion (closed end o f cylin d er).
3. Stack and in stall secondary piston spring, p ressu re
cup and piston in cylin d er bore.
4. Install piston
s crew enters cylin d er bore behind re a r of piston.
5. A ssem ble and in sta ll p rim a ry piston parts in c y lin ­
d er bore.
6. Install stop plate in cylin d er bore.
7. C om press a ll parts in cylin d er bore and in sta ll r e ­
tainer ring in groove.
8. Install r e s e r v o ir c o v e r and seal.
BLEEDING TOOL
A special tool fo r bleeding the SA-40-50 main cylin der
is shown in F igu re 33.
It w ill be n ecessa ry fo r the serv ic e man to install his
own b lee d er adapter fitting to this tool. When bleeding
the system , always bleed the fram e mounted b o o sters
b efo re bleeding any wheel cylinders.
Follow procedu re under " Vacuum P ow er Brake U nits"
in this section.
BRAKE C O M PO N EN TS-SE LF ADJUSTING
FRONT A N D REAR BRAKES (Fig. 3 4 )
Brake shoe adjustment takes place when brakes are
applied with a fir m pedal effo rt while veh icle is backing
up. Applying the brakes m oves an actuator which turns
the star wheel and lengthens the adjusting screw a ssem -
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(
■fr
F ig . 3 3 —Tool fo r B leedin g 4 0 -6 0 Dual C y lin d e r
Inspect cylin d er bore fo r
stop bolt and gasket, making sure
CHEVROLET TRUCK SERVICE MANUAL
BRAKES 5-19