Chevrolet 1977 light duty truck Service Manual page 393

P ro b a b le C ause
1 . I n s u f f i c i e n t f l u i d i n pump
r e s e r v o i r .
P ro b a b le Cause
1 . R e s t r i c t i o n i n g e a r o r b o o s t e r
r e t u r n l i n e s .
AC C U M U L A TO R L E A K D O W N - SYSTEM DOES N O T HOLD CHARGE
P relim inary Check
Start engine and turn the steering wheel until the wheels contact the wheel stops lightly. Hold fo ra
maximum of five seconds. Then release the steering wheel and turn off the engine.
Depress and release the brake pedal. There should be a minimum of three power assisted brake
applications before a hard pedal is obtained.
Re-start the engine and turn the steering wheel until the wheels contact the wheel stops lightly. There
should be a light hissing sound as the accumulator is charged. Hold steering wheel lightly against stop for
a maximum of five seconds. Then release the steering wheel, and turn off the engine.
Wait one hour and apply brake pedal (do not re-start the engine). There should still be a minimum of
three power assisted brake applications before obtaining a hard pedal.
If either of these preliminary checks shows that the accumulator is not holding its charge, the trouble
may be one of the following causes.
P r o b a b le Cause
1 E x t e r n a l l e a k a g e a t a c c u m u l a t o r .
.
2. I n t e r n a l l e a k a g e i n a c c u m u l a t o r .
3.
I n t e r n a l l e a k a g e a t b o o s t e r a c c u m u l a t o r
v a l v e ( i f a c c u m u l a t o r i s
e x t e r n a l l y o r i n t e r n a l l y ) .
DIAGNOSIS - HYDRO-BOOST SYSTEM
POWER STEERING PUMP NOISE O N BRAKE APPLY
BRAKE PEDAL PULLS D O W N SLIGHTLY O N EN G IN E START
n o t l e a k i n g
R e m e d y
1 . F l u i d l e v e l d e c r e a s e s a p p r o x i m a t e l y
1 / 2 " on b r a k e a p p l j / - r e f i l 1 to
p r o p e r l e v e l . I f f l u i d
l e t v e h i c l e s t a n d f o r a p p r o x i m a t e l y
one h o u r ; t he n b l e e d power s t e e r i n g
h y d r a u l i c s y s t e m a s o u t l i n e d e a r l i e r
i n t h i s s e c t i o n .
R e m e d y
1. R e p l a c e l i n e s o r r e p o s i t i o n
l i n e s t o e l i m i n a t e r e s t r i c t i o n .
R e m e d y
1 R e p l a c e b o o s t e r a s s e m b l y .
.
2 .
R e p l a c e b o o s t e r .
3 .
R e p l a c e a l l b o o s t e r s e a l s and
a c c u m u l a t o r v a l v e s .
i s fo a m y ,