Chevrolet 10 Series 1970 Service Manual page 255

M A IN C YLIN D ER -SIN G LE RESERVOIR TYPE
(Fig. 2 9 )
NOTE: These main cylin d ers are o f the basic
sin gle hydraulic r e s e r v o ir type.
stalled on TA50-60 m odels have two pistons in
the body casting, side by side. One piston p r o ­
vid es a hydraulic assist fo r clutch operation.
Tilt Cab
Removal
1. T ilt cab fo rw a rd and block in place.
2. D isconnect brake and clutch lin es at cylin d er and slip
rubber dust boots o ff cy lin d er tubes.
3. R em ove 3 cylin d er attaching bolts and rem ove c y l­
in der (allow in g brake and clutch pedal push rods to
fa ll lo o s e ).
4. R ep a ir the dual brake and clutch cylin d er as r e ­
quired. See d isassem b ly, inspection and assem bly
p roced u res.
Single Cylinder
1. D isconnect brake pedal return spring.
2. Disconnect the brake hydraulic line at the main c y l­
inder mounted on the cab.
the dash and toe pan.
3. R e m o v e cylin d er
cylin d er.
4. R em ove c o v e r fro m
fluid.
Disassembly (Fig. 29 )
Dual Cylinder
Brake Cylinder Side
1. R em ove piston stop snap ring.
2. R em ove piston, p rim a ry cup, cup expander, piston
return spring, check va lv e
Clutch Cylinder Side
R em ove same as brake cylin d er side except fo r r e ­
m oval o f check va lve and check v a lv e seat.
Single Cylinder
1. R em ove lock ring, secondary cup and piston from
main cylin d er.
2. R em ove the p rim a ry cup, spring va lve assem bly and
va lv e seat.
3. R em ove r e s e r v o ir c o v e r and gasket fro m top o f main
cylin d er.
Inspection and Repair
Clean a ll d irt and gre a s e fro m the main cylin d er with
denatured alcohol.
1. Wash a ll p arts in clean alcohol. Make sure that in ­
take and com pensating ports in main cylin d er hous­
ing, b le e d e r holes in piston and vent in f i lle r cap are
clean and open.
NOTE: B efo re washing p arts, hands must be
clean. Do not wash hands in gasoline o r o il b e ­
fo r e cleaning p arts.
clean hands.
2. Inspect cylin d er b o res to make sure they a re smooth.
3. Inspect p rim a ry and secondary cups, va lve and va lve
seat fo r damage o r sw ellin g.
p arts is due to the use o f im p rop er brake fluid o r
washing parts in gasoline o r kerosene.
C ylin d ers in ­
A lso disconnect lines at
retaining bolts and rem ove
top of cylin d er and dump out
and check va lve
Use soap and w ater to
Sw elling o f rubber
NOTE:
The p rim a ry cup has a brass support
ring vulcanized in its base to prevent it fro m
imbedding in the b leed er holes during braking
action.
4. Check piston
clearance between piston and w all of the cylin der
should be fro m .001" to .005".
5. Replace parts as required.
6. Check clearan ce between the edge o f the p rim a ry cup
and the edge of the compensating port. T o check this
clearan ce, p roceed as follow s:
a. P la ce spring assem bly in the housing bore with
the stamped reta in er toward the open end o f the
bore.
b. P la ce p rim a ry cup o v e r the spring, with the fla t
side outward.
c. Using the piston push the cup inward su fficien tly
to allow assem bly o f the piston stop snap ring,
then re le a s e piston against snap ring.
d. Check clearance between the end o f the piston and
the snap ring.
minimum. If the clearance is le s s than .022, the
p rim a ry cup should be replaced.
Assem bly (Fig.
29 )
Dual Cylinder
Brake Cylinder Side
NOTE:
M oisten a ll parts except snap ring with
brake fluid as a ssem bly p ro g resses.
1. C a refu lly position check va lve seat at outlet end of
cylin d er bore.
2. In sert check va lve; then the piston return spring with
p rim a ry cup expander toward open end of cylin der.
seat.
3. Install p rim a ry cup, sk irt fir s t. Take ca re that sk irt
is not ro lled back o r torn during installation.
4. Insert piston with secondary cup toward open end o f
cylin d er. Same ca re to be observed on secondary cup
as on p rim a ry.
5. Install piston stop snap ring.
Clutch Cylinder Side
Replace same as brake cylin d er except fo r replacem ent
o f check va lve and check va lve seat.
Single Cylinder
NOTE:
M oisten a ll parts except snap ring with
brake fluid as assem b ly p ro g resses.
1. Install va lve seat, va lve, spring, and p rim a ry cup in
cylin d er b ore.
2. Install piston and secondary cup; secu re with lock
ring.
Installation
Dual Cylinder (Except Tilt Cab)
1. R everse above applicable rem oval procedu res.
2. F ill main cylin d er r e s e r v o ir and bleed brakes as
outlined in this section.
3. Check operation o f brakes and clutch.
4. In stall co v e r on main cylin der.
Tilt C ab
1. A lign pedal
mounting flange and bolt in place.
fit in cylin der b ore (fig .
This clearan ce should be
push rods, position cylin d er against
CHEVROLET TRUCK SERVICE MANUAL
BRAKES 5-17
30). The
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