Chevrolet 1977 light duty truck, Service Manual

Page: 389 / 861

C O N D IT IO N POSSIBLE CAU SE C O R R E C TIO N
D ra g g in g Brakes
(A very lig h t d ra y is
p resent in a ll disc
b ra k e s im m e d ia te ly a ft e r
p e d a l is r e le a s e d .) — C o n tin u e d
3 . Incorrect p a rk in g b ra k e
a d ju s tm e n t on re a r b rakes.
3 . C heck a n d re a d ju s t to
correct s p ecification s.
4 . C heck v a lv e in s ta lle d in
o u tle t to fro n t disc
b rakes.
4 . C heck m aster c y lin d e r o u tle t
a n d rem ove check valve if
p resent.
G r a b b in g or U n even
B ra k in g Action
1. A ll con dition s listed
u n d er "PULLS".
1. A ll corrections listed
u n d e r "PULLS".
2. M a lfu n c tio n o f c o m b in a tio n
v a lve .
2. R e p la c e a n d b le e d system.
3 . M a lfu n c tio n o f p ow er
b ra k e u nit.
3 . C heck o p e ra tio n a n d
r e p a ir , if necessary.
4 . B in d in g b ra k e p e d a l
mechanism .
4 . C heck a n d lu b ric a te , if
necessary. Possibly re p la c e
p e d a l bushing a n d /o r
spacer.
Pulsation (roughness)
F elt d u rin g norm al
b ra k e a p p lic a tio n .
1. Uneven p a d w e a r caused
b y c a lip e r not s lid in g
d u e to im p ro p e r c le a r ­
ance or d irt.
1. Remove c a lip e r a n d correct
as necessary.
2. Uneven ro tor w e a r
causing a thickness
v a ria tio n b e tw e e n the
two b ra k in g surfaces.
2 . M a c h in e rotors as follow s:
a . M a c h in e rotors to o b ta in a
c irc u m fe re n tia l thickness v a ria tio n no
g r e a te r th a n .0 0 0 5 " in 3 6 0 ° a n d a
la te r a l runout no g r e a te r th a n .0 0 4 "
(m a x . ra te o f c h a n g e not ex c ee d .0 0 1 "
in 3 0 °).
b. C heck c a lip e r freeness. W ith rotor
re m oved , install c a lip e r a n d m ounting
bolts (pins). C heck f o r . 0 0 5 " - .0 1 2 "
c le a ra n c e a t both to p a n d bottom o f
c a lip e r . If less th a n .0 0 5 " is fo u n d , f ile
w ith a f l a t f ile until a t least .0 0 5 " is
o b ta in e d . D O N O T EXCEED A
M A X IM U M o f .0 1 2 " p e r e nd or .0 2 4 "
to ta l c le a ra n c e . C a lip e r c le a ra n c e to
in b o a rd a n d o u tb o a rd re a c tio n pads
must b e e q u a l w ith in .0 0 4 " both a t the
to p a n d bottom o f the c a lip e r . This is to
ensure correct a lig n m e n t o f c a lip e r to
knuckle d u rin g a b ra k e a p p lic a tio n .
c. Remove c a lip e r a ft e r freeness check.
C le a n pins a n d sleeves, re p la c e " O "
rings, a n d a p p ly o lig h t c o a tin g o f
silicone g re a s e or e q u iv a le n t to a ll
contact points a n d " O " rings.