Subaru Legacy IV (2008 year). Manual - part 973

PS-54

General Diagnostic Table

POWER ASSISTED SYSTEM (POWER STEERING)

10.General Diagnostic Table

A: INSPECTION

1 If the tires or wheels are wider than standard, the load to the power steering system is increased. Accordingly, in a condition,

for example before fluid warms-up, relief valve may work before reaching maximum turning angle. In this case, steering effort
may be heavy. When the measured hydraulic pressure is normal, there is no abnormal thing.

2 In cold weather, steering effort may be heavy due to increased flow resistance of cold fluid. After warming-up engine, turn the

steering wheel from stop to stop several times to warm up fluid. If steering effort reduces normally, function is normal.

3 In cold weather or with insufficient warm up of the engine, steering effort may be heavy due to excessive drop of idle rpm when

turning the steering wheel. In this case, start the vehicle with increasing engine speed than usual. If steering effort reduces nor-
mally, function is normal.

Trouble

Possible cause

Corrective action

• Steering effort is heavy in all
ranges.
• Steering effort is heavy at
stand still.
• Steering wheel vibrates
when turning.

1. Pulley belt
• Unequal length of pulley belts
• Contact with oil or grease
• Looseness or damage of the pulley belt
• Poor uniformity of the pulley belt cross section
• Pulley belt touches to pulley bottom
• Poor revolution of pulleys (except oil pump pulley)
• Poor revolution of oil pump pulley

Adjust or replace.

2. Tire and wheel
• Improper tire out of specifications

• Improper wheel out of specifications

• Tires not properly inflated

Replace or reinflate.

3. Fluid
• Low fluid level
• Air entry in fluid
• Dust entry in fluid
• Fluid deterioration
• Inadequate warm up of fluid

Refill, bleed air, replace or
instruct customer.

4. Idle speed
• Lower idle speed
• Excessive drop of idle speed at start or when turning the steer-
ing wheel

Adjust or instruct customer.

5. Measure the hydraulic pressure. <Ref. to PS-48, INSPECTION,
Oil Pump.>

Replace the problem parts.

6. Measure the steering wheel effort. <Ref. to PS-57, MEASUREMENT
OF STEERING EFFORT, INSPECTION, General Diagnostic Table.>

Adjust or replace.

• Vehicle leads to one side or
the other
• Returning force of steering
wheel to center is poor.
• Steering wheel vibrates
when turning.

1. Fluid line
• Folded hose
• Flattened pipe

Repair or replace.

2. Tire and wheel
• Flat tire
• Mixed use of different tires
• Mixed use of different wheels
• Abnormal wear of tire
• Unequal tread remaining
• Unequal pressure of tire

Adjust, fix or replace.

3. Front alignment
• Improper or unequal caster
• Improper or unequal toe-in
• Loose suspension connections

Adjust or retighten.

4. Others
• Damaged joint assembly
• Unbalanced height
• Unbalanced weight

Replace, adjust or instruct
customer.

5. Measure the steering wheel effort. <Ref. to PS-57, MEASUREMENT
OF STEERING EFFORT, INSPECTION, General Diagnostic Table.>

Adjust or replace.

PS-55

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 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

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 five seconds or more.)

Normal operation

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-42, INSPECTION,
Pipe Assembly.>

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 at engine ON or OFF.

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.
(Replace two belts as a set.)

Warpage or dirty V-groove surface of oil pump pulley

Clean or replace.

PS-56

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

Correct 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.

Torque converter growl, air conditioner compression growl

Remove the power steering pul-
ley belt and check.

Grinding noise (continuous)
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-57

General Diagnostic Table

POWER ASSISTED SYSTEM (POWER STEERING)

2. MEASUREMENT OF STEERING EFFORT

Step

Check

Yes

CHECK STEERING EFFORT.
1) Stop the vehicle on paved road.
2) Start the engine.
3) Idle the engine.
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 more, steer-
ing 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
29.4 N (3.0 kgf, 6.6 lb)?

Go to step 2.

Adjust the back-
lash.

CHECK STEERING EFFORT.
1) Stop the engine.
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
294.2 N (30 kgf, 66.2 lb)?

Go to step 3.

Perform the adjust-
ment.

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 lb)?

Go to step 4.

Check, adjust and
replace if neces-
sary.

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.

Check, adjust and
replace if neces-
sary.

CHECK UNIVERSAL JOINT.
Measure the swing torque of the joint (yoke of
steering column side). <Ref. to PS-15,
INSPECTION, Universal Joint.>

Is the swing torque of the uni-
versal joint less than 7.3 N
(0.74 kgf, 1.64 lb)?

Go to step 6.

Replace with a
new part.

CHECK UNIVERSAL JOINT.
Measure the swing torque of the joint (yoke of
gearbox side). <Ref. to PS-15, INSPECTION,
Universal Joint.>

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

Go to step 7.

Replace with a
new part.

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.

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

If the tie-rod ends of suspen-
sion have unsteady revolution
or rattling?

Inspect and
replace if neces-
sary.

Go to step 9.

CHECK BALL JOINT.
Remove the ball joint.

If the ball joints of suspension
have unsteady revolution or rat-
tling?

Inspect and
replace if neces-
sary.

Go to step 10.

CHECK GEARBOX.
Measure the rotating of gearbox.
<Ref. to PS-35, TURNING RESISTANCE OF
GEARBOX, INSPECTION, Steering Gearbox.>

Is the rotating resistance of steer-
ing gearbox less than 11.3 N
(1.15 kgf, 2.54 lb)? Is the differ-
ence between right and left
sides less than 24%?

Steering effort is
normal.

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

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