Chevrolet 70 1969 Series, Shop Manual

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SECTION 5
BRAKES
CONTENTS OF THIS SECTION
Page
V acuum Pow er Brake S y s te m ............................................5-1
V acuum Pow er Cylinder Application C h a r t .............5-1
O v e rh a u l.................................................................................. 5-1
Pow er Cylinder (Tandem D ia p h ra g m )............... 5-1
Pow er Cylinder (Single D ia p h ra g m )..................5-3
Air B ra k e s ................................................................................5-6
O v e rh a u l....................................................................................... 5-6
Slack A d ju ste r..................................................................... 5-6
S tandard Brake C h a m b e rs ............................................5-7
S tandard Stopm aster Brake C h a m b e rs ..................5-8
DD3 Brake A ctuator C h a m b e r....................................5-9
Application V alv es..............................................................5-11
Relay V a lv e .............................................................................5-13
Pressure Protection V a lv e.............................................. 5-13
M oisture Ejector V a lv e ................................................... 5-14
Trailer Brake H and C ontrol V alv es..........................5-15
Tilt C a b ................................................................................5-15
Page
C on v en tio nal......................................................................5-17
Limiting Quick Release V a lv e .......................................5-19
Trailer Emergency Air Valve - Tilt C a b ..................5-20
Trailer Emergency Air Supply C ontrol V alves. . .5-21
T ractor Protection (Breakaw ay) V alv es..................5-22
Inversion V alv e......................................................................5-24
Quick Release V a lv e ...........................................................5-24
Synchro V alv e........................................................................5-24
M -R Air Supply V a lv e ......................................................5-25
B-W Air Supply Valve (models PP-1 and P Q -3 ). 5-25
B-W Air Supply Valve (model P P - 2 ) ..........................5-26
Safety V a lv e .............................................................................5-27
Check V alv es...........................................................................5-27
Air C om pressor and G o v e rn o rs.........................................5-30
M idland-Ross T y p e ..............................................................5-30
Bendix-W estinghouse T u-Flo T y p e ............................ 5-44
VACUUM POWER BRAKE SYSTEM
R efer to Figures 1 and 2 for a typical Illustration of a vacuum power brake system on conventional cab and tilt cab models.
V A CU U M POWER CYLINDER MODEL APPLICATION CHART
Truck Power Cyl. Power Cyl. Truck Power Cyl. Power Cyl.
Model Model Type Model Model Type
70 Series
(Single Rear Axle-
Conventional) C-4035-A
Single
Diaphragm
70 Series
(Tandem Rear Axle-
Conventional)
70 Series (Tilt Cab)
C-4036-A
C-4058
Tandem
Diaphragm
Tandem
Diaphragm
OVERHAUL
POWER CYLINDER OVERHAUL
(TANDEM DIAPHRAGM )
DISASSEMBLY (Fig. 3)
1. Scribe m arks on rear diaphragm housing, front and
rear housing assembly, front housing and clam p
bands. Scribe m arks on front diaphragm housing and
hydraulic cylinder body. Scribe m arks on control
valve housing and hydraulic cylinder body.
2. R em ove bleeder screw (where used).
3. M oun t unit in vise with vacuum cham bers up and vise
jaw s gripping the hydraulic cylinder body. Tighten
vise only enough to hold the unit, do not tighten vise
enough to distort the hydraulic cylinder body.
4. Rem ove clam p band and rear housing.
5. Rem ove by-pass tube.
C A U TIO N : O uter e d g e o f diaphragm plates are
very sh a rp a n d can cause se ve re cut if not pro­
perly h and led. Rem ove jam nut from push rod.
S cre w push rod out o f en d plug a n d allo w it to
drop inside o f the assem bly.
6. Rem ove tube and nut assembly.
7. R em ove front clam p band and lift front and rear
housing assem bly off front housing.
8. R em ove end plug from rear end of piston rod.
9. R em ove diaphragm and plate assembly, collar and di­
aphragm return spring.
10. Rem ove snap ring from piston rod.
11. Rem ove front diaphragm and plate assem bly with
piston rod and nut.
12. R em ove nut from piston rod and remove diaphragm
and plate assembly.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M A N U A L