Chevrolet 1977 light duty truck Service Manual page 389

C O N D IT IO N
D ra g g in g Brakes
(A very lig h t d ra y is
p resent in a ll disc
b rakes im m e d ia te ly a fte r
p e d a l is re le a s e d .) — C o n tin u e d
G ra b b in g or Uneven
B rak in g Action
Pulsation (roughness)
Felt d u rin g norm al
b ra k e a p p lic a tio n .
POSSIBLE CAUSE
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.
4 . Check va lve in s ta lle d in
o u tle t to fro n t disc
b rakes.
1. A ll conditions listed
u n d er "PULLS".
2. M a lfu n c tio n of com bin atio n
v alve.
3 . M a lfu n c tio n o f pow er
b ra k e unit.
4 . B in d in g b ra k e p e d a l
mechanism.
1. Uneven p a d w e a r caused
by c a lip e r not slidin g
d u e to im p ro p e r c le a r­
ance or d irt.
2. Uneven rotor w e a r
causing a thickness
v a ria tio n b etw e e n the
two b ra k in g surfaces.
C O R R E C TIO N
3 . Check a n d re a d ju s t to
correct specifications.
4 . C heck m aster c y lin d e r o u tlet
a n d rem ove check valve if
present.
1. A ll corrections listed
u n d e r "PULLS".
2. R eplace a n d b le e d system.
3 . Check o p e ra tio n a n d
r e p a ir, if necessary.
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.
1. Remove c a lip e r a n d correct
as necessary.
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 re 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 re a te r th a n .0 0 4 "
(m ax. ra te o f c h a n g e not exceed .0 0 1 "
in 3 0 °).
b. C heck c a lip e r freeness. W ith rotor
rem oved, install c a lip e r a n d m ounting
bolts (pins). C heck f o r
c le a ra n c e a t both top a n d bottom o f
c a lip e r. If less than .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 of .0 1 2 " p e r end 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 reactio n pads
must b e e q u a l w ithin .0 0 4 " both a t the
top a n d bottom o f the c a lip e r. This is to
ensure correct a lig n m e n t of 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 fte 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.
.0 0 5 " -.0 1 2 "