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.

PS-54

General Diagnostic Table

POWER ASSISTED SYSTEM (POWER STEERING)

Sizzling noise (continuous)
While engine is running.

Fluid aeration

Fix the faulty part causing aera-
tion.
Replace the fluid and vent air.

Damaged pipe of gearbox

Replace the pipe.

Faulty inside of hose or pipe
Flattened hose or pipe

Repair or replace.

Abnormal inside of oil tank

Replace.

Removed oil tank cap

Install cap.

Whistle (continuous)
While engine is running.

Faulty pipe of gearbox or faulty hose

Replace the faulty parts of the
gearbox or the hose.

Whine or growl (intermittent or
continuous)
While engine is running (with/
without steering turned).

Looseness of oil pump, oil pump bracket attachment

Retighten.

Fault inside of oil pump or hose

Replace the oil pump or hose, if
the noise can be heard when
vehicle is running as well as
being stopped.

Air conditioner compression whirling noise

Remove the power steering pul-
ley belt and check.

Grinding noise (intermittent)
While engine is running (with the
steering turned).

Fault inside of gearbox

Replace the faulty parts of gear-
box.

Faulty steering shaft bearing

Apply grease or replace.

Occurs when turning the steering wheel with brakes (ser-
vice or parking) applied.

If the noise goes off when brake
is released, it is normal.

Vibration
While engine is running (with/
without steering turned).

Engine speed is too low.

Adjust, and notify customer.

Air in vane pump

Repair faulty part
Vent air.

Damaged valve in oil pump or gearbox

Replace the faulty parts in gear-
box and oil pump.

Excessive play in steering, looseness of suspension parts Retighten.

Trouble

Possible cause

Corrective action

PS-55

General Diagnostic Table

POWER ASSISTED SYSTEM (POWER STEERING)

2. MEASUREMENT OF STEERING EFFORT

Step

Check

Yes

No

1

CHECK STEERING EFFORT.
1) Stop the vehicle on paved road.
2) Start the engine.
3) Run the engine at idle.
4) Install a spring scale on the steering wheel.
5) Pull the spring scale at a right angle to the
steering wheel, and measure both right and left
steering wheel efforts.

NOTE:

When turning the steering more quickly than
necessary from a direction to the other direction
at an engine speed of 2,000 rpm or higher,
steering effort may be heavy. This is caused by
flow characteristic of the fluid in the oil pump
and is not a defect.

Is the steering effort less than
34 N (3.5 kgf, 7.6 lbf)?

Steering effort is
normal.

Go to step

2.

2

CHECK STEERING EFFORT.
1) Stop the engine and lift up the vehicle.
2) Pull the spring scale at a right angle to the
steering wheel, and measure both right and left
steering wheel efforts.

Is the steering effort less than
17 N (1.7 kgf, 3.8 lbf)?

Go to step

3.

Perform the back-
lash adjustment.

3

CHECK STEERING WHEEL EFFORT.
1) Remove the universal joint.
2) Measure the steering wheel effort.

Is the steering effort less than
2.26 N (0.23 kgf, 0.51 lbf)?

Go to step

4.

Replace the steer-
ing column.

4

CHECK STEERING WHEEL EFFORT.
Measure the steering wheel effort.

Is the difference of steering
effort between right and left
less than 20%?

Go to step

5.

Replace the steer-
ing column.

5

CHECK UNIVERSAL JOINT.
Measure the swing torque of the joint (yoke of
steering column side). <Ref. to PS-14,
INSPECTION, Universal Joint.>

Is the swing torque of the uni-
versal joint less than 4.5 N
(0.46 kgf, 1.01 lbf)?

Go to step

6.

Replace the uni-
versal joint.

6

CHECK UNIVERSAL JOINT.
Measure the swing torque of the joint (yoke of
gearbox side). <Ref. to PS-14, INSPECTION,
Universal Joint.>

Is the swing torque of the uni-
versal joint less than 3.8 N
(0.39 kgf, 0.86 lbf)?

Go to step

7.

Replace with a
new part.

7

CHECK FRONT WHEEL.
Check the front wheels.

Does the front wheels have
unsteady revolution or rattling,
or does the brake drag?

Inspect, readjust
and replace if nec-
essary.

Go to step

8.

8

CHECK TIE-ROD ENDS.
Remove the tie-rod ends from housing.

Does the tie-rod ends have
unsteady revolution or rattling?

Inspect and
replace if neces-
sary.

Go to step

9.

9

CHECK GEARBOX.
Measure the rotating of gearbox.
<Ref. to PS-36, TURNING RESISTANCE OF
GEARBOX, INSPECTION, Steering Gearbox.>

Is the turn resistance of the
steering gearbox less than 13.7
N (1.40 kgf, 3.08 lbf)? Is the dif-
ference between the right and
left rotational resistances less
than 24%?

Steering effort is
normal.

Readjust the back-
lash, and if ineffec-
tive, replace the
faulty parts.

PS-01008

PS-56

General Diagnostic Table

POWER ASSISTED SYSTEM (POWER STEERING)

10

CHECK GEARBOX.
Measure the sliding of gearbox.
<Ref. to PS-35, SERVICE LIMIT, INSPEC-
TION, Steering Gearbox.>

Is the sliding resistance of the
steering gearbox less than 343
N (35 kgf, 77 lbf)? Is the differ-
ence between the right and left
sliding resistances less than
20%?

Steering effort is
normal.

Readjust the back-
lash, and if ineffec-
tive, replace the
faulty parts.

Step

Check

Yes

No