Noise And Vibration - Subaru IMPREZA 2004 Service Manual

POWER ASSISTED SYSTEM (POWER STEERING)

1. NOISE AND VIBRATION

CAUTION:
Don't keep the relief valve operated over 5 seconds 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 char-
acteristic 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 provided that the noise elim-
inates when the vehicle is running.
• When turning the steering wheel with service brake and/or parking brake applied, the noise is generated
by creaking between disk and pads. However this does not indicate abnormal function in system.
• There may be a little vibration around the steering devices when turning steering wheel at standstill, 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 be-
cause of combined conditions, i.e., road surface and tire surface, engine speed and turning speed of steering
wheel, fluid temperature and braking condition.
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 transmission vehicle.
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-88
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.