Noise And Vibration - Subaru Impreza 2003 Service Manual

POWER ASSISTED SYSTEM (POWER STEERING)

1. NOISE AND VIBRATION

CAUTION:
Don't keep the relief valve operated over 5 sec-
onds at any time or inner parts of the oil pump
may be damaged due to rapid increase of fluid
temperature.
NOTE:
• Grinding noise may be heard immediately after
the engine start in extremely cold condition. In this
case, if the noise goes off during warm-up there is
no abnormal function in the system. This is due to
the fluid characteristic in extremely cold condition.
• Oil pump makes whine or growl noise slightly
due to its mechanism. Even if the noise can be
heard when steering wheel is turned at stand still
there is no abnormal function in the system provid-
ed that the noise eliminates when the vehicle is
running.
• When turning the steering wheel with service
brake and/or parking brake applied, the noise is
Trouble
Hiss noise (continuous)
While engine is running.
Rattling noise (intermittent) While
engine is running.
Knocking
When turning steering wheel in
both direction with small angle
repeatedly at engine ON or OFF.
Grinding noise (continuous)
While engine is running.
Squeal, squeak (intermittent or
continuous)
While engine is running.
GENERAL DIAGNOSTIC TABLE
Possible cause
Relief valve emits operating sound when steering wheel is
completely turned in either direction. (Don't keep this con-
dition over 5 seconds.)
Relief valve emits operating sound when steering wheel is
not turned. This means that the relief valve is faulty.
Interference with adjacent parts
Loosened installation of oil pump, oil tank, pump bracket,
gearbox or crossmember
Loosened installation of oil pump pulley or other pulley(s)
Loosened linkage or play of steering or suspension Loos-
ened tightening of joint or steering column
Sound generates from the inside of gearbox or oil pump.
Excessive backlash
Loosened lock nut for adjusting backlash
Loosened tightening or play of tie-rod, or tie-rod end
Vane pump aeration
Vane pump seizing
Pulley bearing seizing of oil pump
Folded hose, flat pipe
Maladjustment of pulley belt
Damaged or charged pulley belt
Unequal length of pulley belts
Run out or soilage of V-groove surface of oil pump pulley
PS-90
generated by creaking between disk and pads.
However this does not indicate abnormal function
in system.
• There may be a little vibration around the steer-
ing devices when turning steering wheel at stand-
still, even though the component parts have no
defects.
Hydraulic systems are likely to generate this kind of
vibration as well as working noise and fluid noise
because of combined conditions, i.e., road surface
and tire surface, engine speed and turning speed of
steering wheel, fluid temperature and braking con-
dition.
This phenomena does not indicate there is some
abnormal function in the system.
The vibration can be known when steering wheel is
turned repeatedly at various speeds from slow to
rapid step by step with parking brake applied on
concrete road and in "D" range for automatic trans-
mission vehicle.
Corrective action
Normal
Defective
Replace the oil pump.
Check the clearance.
Correct if necessary.
<Ref. to PS-69, INSPECTION,
Pipe Assembly [LHD MODEL].>
Retighten.
Retighten.
Retighten or replace.
Replace the faulty parts of gear-
box or oil pump.
Adjust and retighten.
Retighten or replace.
Inspect and retighten the fluid
line connection.
Refill fluid and vent air.
Replace the oil pump.
Replace the oil pump.
Replace.
Adjust or replace.
(Replace two belts as a set.)
Clean or replace.