Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 583
PS-53
General Diagnostic Table
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 by applying the parking brake on a concrete surface and turning the steering wheel from
slowly to rapidly, in steps.
Trouble
Possible cause
Corrective action
Hiss noise (continuous)
While engine is running.
Relief valve emits operating sound when steering wheel is
completely turned in either direction. (Do not keep this
condition for 5 seconds or more.)
Normal
Relief valve emits operating sound when steering wheel is
not turned. This means that the relief valve is defective.
Replace the oil pump.
Rattling noise (intermittent)
While engine is running.
Interference with adjacent parts
Check the clearance.
Correct if necessary.
<Ref. to PS-57, INSPECTION
OF CLEARANCE, INSPECTION,
General Diagnostic Table.>
Loosened installation of oil pump, oil tank, pump bracket,
gearbox or crossmember
Retighten.
Loose oil pump pulley or other pulley(s)
Retighten.
Looseness of linkage, play of steering, improper tightening
(looseness) of suspension joint or steering column
Retighten or replace.
Sound generates from the inside of gearbox or oil pump.
Replace faulty parts in the gear-
box or oil pump.
Knocking
When turning steering wheel in
both directions with small angle
repeatedly while the engine is
running.
Excessive backlash
Loosened lock nut for adjusting backlash
Adjust and retighten.
Insufficient tightening or play in the tie-rod or tie-rod end
Retighten or replace.
Grinding noise (continuous)
While engine is running.
Air in vane pump
Inspect and retighten the fluid
line connection.
Refill the fluid and vent air.
Vane pump seizing
Replace the oil pump.
Oil pump pulley bearing seized
Replace the oil pump.
Folded hose, flattened pipe
Replace.
Squeal, squeak (intermittent or
continuous)
While engine is running.
Improper adjustment of pulley belt
Damaged or over tensioned pulley belt
Unequal length of pulley belts
Adjust or replace.
Runout or dirty V-groove surface of oil pump pulley
Clean or replace.