Noise And Vibration - Subaru 2009 IMPREZA Service Manual

POWER ASSISTED SYSTEM (POWER STEERING)

1. NOISE AND VIBRATION

CAUTION:
Do not keep the relief valve operated for five seconds or more at any time or inner parts of the oil
pump may be damaged due to rapid increase of fluid temperature.
NOTE:
• A screeching noise may be heard immediately after the engine start in extremely cold conditions. 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
characteristics in extremely cold condition.
• The oil pump normally makes a small whining noise due to its mechanism. Even if a noise is heard when
steering wheel is turned at stand still, there is no abnormal function in the system provided that the noise
eliminates when the vehicle is driving.
• When turning the steering wheel with the brake applied when the vehicle is parked, a screeching noise
may be generated by the brake disc and pads. This is not a fault in the steering system.
• There may be a small vibration around the steering devices when turning the steering wheel at standstill,
even though the component parts are operating properly.
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.
These conditions do not indicate a problem in the system.
Confirm vibration for an AT model, by applying the parking brake on a concrete surface, shifting into the "D"
range, and turning the steering wheel repeatedly from slow to rapid, step by step.
Trouble
Hiss noise (continuous)
While engine is running.
Rattling noise (intermittent)
While engine is running.
Knocking
When turning steering wheel in
both directions 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. (Do not keep this con-
dition for 5 seconds or more.)
Relief valve emits operating sound when steering wheel is
not turned. This means that the relief valve is defective.
Interference with adjacent parts
Loosened installation of oil pump, oil tank, pump bracket,
gearbox or crossmember
Loose oil pump pulley or other pulley(s)
Looseness of linkage, play of steering, improper tightening
(looseness) of suspension joint or steering column
Sound generates from the inside of gearbox or oil pump.
Excessive backlash
Loosened lock nut for adjusting backlash
Insufficient tightening or play in the tie-rod or tie-rod end
Air in vane pump
Vane pump seizing
Oil pump pulley bearing seized
Folded hose, flattened pipe
Improper adjustment of pulley belt
Damaged or over tensioned pulley belt
Unequal length of pulley belts
Runout or dirty V-groove surface of oil pump pulley
PS-52
Corrective action
Normal operation
Replace the oil pump.
Check the clearance.
Correct if necessary.
<Ref. to PS-56, INSPECTION OF
CLEARANCE, INSPECTION,
General Diagnostic Table.>
Retighten.
Retighten.
Retighten or replace.
Replace faulty parts in the gear-
box or oil pump.
Adjust and retighten.
Retighten or replace.
Inspect and retighten the fluid line
connection.
Refill the 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.