Chevrolet 10 Series 1970 Service Manual page 251

F i g . 2 4 — U s in g D r u m - t o - S h o e C l e a r a n c e G a u g e T o o l J — 2 1 1 7 7
NOTE: A ll brake
attaching parts in
perform an ce o f v ita l components and system s,
and/or could resu lt in m ajor
They must be replaced with p arts of the same
p a rt numbers o r with equivalent parts i f r e ­
placem ent becom es n ecessa ry. Do not use r e ­
placem ent parts o f le s s e r quality o r substitute
design. Torque values must be used as specified
during reassem b ly to assure p ro p er retention of
these parts.
M A IN C Y L IN D E R -D U A L SYSTEM
NOTE: This m odel
C A -K A -P A 1 0 -2 0 , and C A -P A 3 0 s e r ie s v eh icles.
When s e rv ic e p roced u res fo r C E -C S-50-60 s e ­
rie s m odels a re requ ired , r e fe r to "M a in C y l­
in d e r-S in g le R e s e r v o ir Type o r Fram e Mounted
booster.
When s e rv ic in g the dual m aster cylin d er, follo w the
ru les below when replacin g eith er com plete m aster c y l­
in der o r the component pistons o f the cylin d er.
equally im portant to use only the c o r r e c t s e r v ic e parts
when s e rv ic in g a main cylin d er.
The dual main cylin d er used on light trucks is designed
and built to satisfy individual brake system displacem ent
requ irem en ts fo r each veh icle
n ecessary that c o r r e c t parts be used when replacing
eith er com plete main cylin d er assem b lies o r the com ­
ponent pistons of these assem b lies.
Th ere are three sources fo r dual main cylin ders.
D elco M oraine, Bendix and W agner E le c tric . The Bendix
unit can be read ily id en tified by a " Secondary Piston
SERVICE OPERATIONS
attachments a re im portant
that they could a ffect the
rep a ir expense.
cy lin d er is installed on
lin e. T h e re fo re , it is
F ig . 2 5 —C h e ckin g Brake Shoe Lin in g C le a ra n ce using Tool J — 21177
Stop" bolt on the bottom of the casting. D elco M oraine
main cylin d ers do not have this bolt exposed. W agner
E le c tric uses a bolt to secure its cover.
The length of the secondary pistons in these main c y l­
inders is a c r itic a l fa c to r in the displacem ent capabilities
o f a p a rticu la r main cylin der.
a re coded, using rings o r g ro o ves in the shank o r center
section of the piston. R e fe r to the chart below fo r p rop er
identification.
The p rim a ry pistons are of two types. One has a deep
socket fo r the push rod and the other a v e ry shallow
socket.
It is mandatory that replacem ent pistons be identical
to the orig in a l piston.
the identification m arks on the secondary piston and the
socket contour o f the push rod end of the p rim a ry piston.
M A IN C Y LIN D E R -LIG H T TRUCKS (Fig. 2 8 )
NOTE: A lw ays use denatured alcohol o r brake
fluid to clean any main cylin der o r wheel c y l­
inder parts o r when flushing a brake system .
It is
CAUTIO N:
C LE A N IN G
KEROSENE, C A R B O N -T E T R A C H L O R ID E , A C E ­
TONE, P A IN T
N A TU R E AS THESE SO LVENTS D E T E R IO R A T E
RUBBER P A R T S , CAUSING THEM TO BECOME
SO FT AND
SHORT T IM E .
1. The length o f the component pistons in the m aster
cylin d ers are c r itic a l fa cto rs in displacem ent capa­
b ilitie s o f
These secondary pistons
This can be v e r ifie d by checking
N E V E R USE M I N E R A L - B A S E
S O L V E N T SUCH AS GASO LINE,
T H IN N E R OR UNITS OF LIK E
S W O LLE N IN AN E X T R E M E L Y
a p a rticu la r m aster cylin d er.
CHEVROLET TRUCK SERVICE MANUAL
BRAKES 5-13
These