Table of Contents
Advertisement
•
STEERING
19-39
POWER STEERING PUMP SERVICE
INDEX
Page
Fluid Level
39
Hose—Removal/Installation
. . . . . . . . . . . . . . . . . . 45
Operation
39
Pressure Test
44
Page
Pump—Removal/Installation
4 6
Pump Repair Service
46
Service Diagnosis
3 9
OPERATION
Rectangular
p u m p vanes rotated b y t h e shaft
d r i v e n rotor move t h e fluid from t h e i n t a k e t o t h e
cam r i n g pressure cavities. As t h e rotor begins to
t u r n , centrifugal force moves t h e vanes against t h e
inside surface of t h e cam r i n g to p i c k u p residual
fluid.
T h i s fluid is t h e n forced i n t o t h e h i g h pressure
area. A s more fluid is picked up by t h e vanes, fluid is
forced i n t o t h e cavities of the t h r u s t plate t h r o u g h
t w o crossover holes i n t h e cam r i n g a n d pressure
plate. T h e crossover holes empty i n t o t h e h i g h pres-
sure area between t h e pressure plate a n d t h e hous-
i n g end cover.
W h e n t h e h i g h pressure area is
filled,
fluid
flows
under t h e vanes i n t h e rotor slots, forcing t h e vanes
to follow t h e inside oval surface of the c a m r i n g . As
the vanes reach t h e restricted area o f the c a m r i n g ,
fluid
is forced out f r o m between the vanes. W h e n ex-
cess fluid flow is generated d u r i n g high-speed opera-
t i o n , a regulated amount of fluid r e t u r n s to t h e pump
i n t a k e side t h r o u g h t h e flow control valve. T h e flow
control valve reduces the power required t o d r i v e t h e
p u m p and reduces temperature " b u i l d - u p " .
W h e n steering conditions cause t h e m a x i m u m a l -
lowable safe pressure to be exceeded (e.g., t u r n i n g
the wheels against t h e steering "stops") t h e pressure
b u i l t u p i n t h e steering gear also exerts pressure on
the s p r i n g end of the flow control valve. T h i s end of
the valve houses the pressure relief valve. H i g h pres-
sure l i f t s t h e relief valve b a l l from i t s "seat" and a l -
lows fluid t o flow t h r o u g h a trigger orifice located i n
t h e outlet
fitting.
T h i s reduces t h e pressure on t h e
spring e n d o f t h e flow control valve, w h i c h t h e n
opens a n d allows t h e fluid t o r e t u r n t o t h e i n t a k e
side o f t h e pump. T h i s action l i m i t s t h e m a x i m u m
pressure o u t p u t of the pump to a safe level.
W i t h n o r m a l operating conditions, t h e pressure re-
quirements o f the p u m p are below m a x i m u m , caus-
i n g t h e pressure r e l i e f valve to r e m a i n closed.
S a f e t y
g o g g l e s s h o u l d b e w o r n a t a l l t i m e s
w h e n i n v o l v e d w i t h p o w e r s t e e r i n g p u m p ser-
v i c e .
A power steering pump can be identified b y i t s
" h a m c a n " shaped reservoir (Fig. 1).
Fig. 1 Power Steering Pump
FLUID LEVEL
CAUTION:
The fluid level should be "checked" with
engine off to prevent injury from moving compo-
nents. Do not use automatic transmission fluid to
supplement the fluid in the reservoir. Do not overfill
the reservoir.
Wipe t h e reservoir filler cap clean of foreign mate-
r i a l , t h e n check t h e f l u i d level ( F i g . 1). The dipstick
should indicate F U L L C O L D w h e n t h e fluid is a t
n o r m a l ambient temperature (approximately 21°C t o
27°C/70°F to 80°F). Replenish t h e fluid, i f necessary,
w i t h M O P A R P o w e r S t e e r i n g F l u i d , P a r t N o .
4318056, o r a n e q u i v a l e n t f l u i d .
SERVICE DIAGNOSIS
There is some noise i n a l l power steering systems.
One o f the most common is a hissing sound most ev-
ident a t vehicle standstill or p a r k i n g . Hiss is a h i g h
frequency noise s i m i l a r t o t h a t experienced
w h i l e
slowly closing a water tap. T h e noise is present i n
every valve and results f r o m h i g h velocity fluid pass-
i n g t h e valve orifice edges. There is no relationship
between this noise a n d performance of t h e steering
pump. " H i s s " can be expected w h e n t h e steering
wheel is a t the end of t r a v e l or w h e n slowly t u r n i n g
the wheels at vehicle s t a n d s t i l l .
Advertisement
Table of Contents
