SUSPENSION SYSTEM DIAGNOSIS/TESTING

id021000800200

Front Suspension Inspection/Verification

Caution
• Always perform a preliminary inspection of the front end components before adjusting the front wheel alignment.

1. Prior to inspection, perform the following procedures:

(1) Fill all fluids to specification.
(2) Make sure that the spare tire and related equipment are correctly stored.
(3) Remove any mud, dirt, or road deposits from the chassis and underbody.
(4) Maintain the vehicle at a normal load. Inflate all tires to the recommended pressure.
(5) Verify that both front tires are the specified size.
(6) Inspect the lower arm ball joints for wear or damage. (See FRONT LOWER ARM INSPECTION.)
(7) Inspect the steering components for wear or damage. (See STEERING SYSTEM DIAGNOSIS/TESTING.)
(8) Inspect the steering gear and mounting bolts and tighten to the specified torque. (See STEERING GEAR AND LINKAGE REMOVAL/INSTALLATION (L.H.D.).) (See STEERING GEAR AND LINKAGE REMOVAL/INSTALLATION [L3](R.H.D.).) (See STEERING GEAR AND LINKAGE REMOVAL/INSTALLATION [YF (2.0 L Zetec), AJ (3.0 L Duratec)](R.H.D.).)

Wheel bearings

1. Inspect the front wheel bearing for seizing or damage.

2. Inspect the wheel hub for cracks or damage to the casting.

Shock absorber and coil spring

1. Visually inspect each component of the shock absorber and spring and replace if necessary. (See FRONT SHOCK ABSORBER AND COIL SPRING REMOVAL/INSTALLATION.) (See REAR SHOCK ABSORBER REMOVAL/INSTALLATION.) (See REAR COIL SPRING REMOVAL/ INSTALLATION.)

2. Inspect the shock absorbers for weepage or leaks. Verify that the oil is not from sources other than the shock absorber.

• Weepage is a condition that:
- deposits a thin film of oil on the shock absorber.
- is normally noticed due to a collection of dust on the shock absorber.
- occurs during the normal break-in period of 4,800-8,050 km {3,000-5,000 mile}. After this period, no new signs of oil should be visible.
- does not require replacement of the shock absorber.
• Leakage is a condition that:
- covers the entire shock absorber with oil.
- will drip oil onto surrounding suspension components.
- requires replacement of the shock absorber.

3. Inspect the shock absorbers using the following procedure:

(1) Remove the suspected shock absorbers. (See FRONT SHOCK ABSORBER AND COIL SPRING REMOVAL/INSTALLATION.) (See REAR SHOCK ABSORBER REMOVAL/INSTALLATION.)
Extend the piston rod when removing the shock absorber.
(2) Compress the LH and RH piston rods. Both should offer the same resistance when compressed.
(3) Compress and release the LH and RH piston rods. The piston rods should extend equally after being released.

4. If any malfunction is found during the above test, replace the shock absorber(s).

Vehicle Inspection

1. Inspect all tires for specified inflation pressure.

2. Inspect the tire condition and verify that the front wheel alignment, wheel balance, and overall tire condition (such as separation or bulging) are normal.

3. Inspect the vehicle for overloading or sagging.

4. Road test the vehicle to verify the customer concern.

5. Replace insulators and bushings with new ones as necessary. Tighten all component parts to the specified torque. (See FRONT SHOCK ABSORBER AND COIL SPRING REMOVAL/INSTALLATION.) (See REAR SHOCK ABSORBER REMOVAL/INSTALLATION.)

Rear Suspension Inspection/Verification

1. At regular intervals, inspect the condition of the rear suspension arms and bushings. Install new parts as necessary.

Symptom Troubleshooting Chart

1. Verify the symptom, and conduct corresponding diagnosis.

Troubleshooting Item

Possible Cause

No.

Drift left or right
• Tire
• Steering gear and linkage
• Wheel alignment
• Brakes system components
1
Steering wheel off-center
• Wheel Alignment
• Steering gear and linkage
• Front lower arm ball joint
2
Tracks incorrectly
• Rear suspension
• Caster
3
Rough ride
• Front shock absorber components
• Rear shock absorber and spring
4
Excessive noise
• Front stabilizer components
• Coil spring
• Suspension components
• Shock absorber
5
Uneven tire wear
• Wheel and tire unbalance
• Tire inflation
• Shock absorber
• Wheel alignment
6
Vibration
• Wheels and tires
• Front drive shaft
• Steering system components
• Shock absorber components
• Coil spring and strut mount
• Hub bolts and wheel nuts
• Front lower arm ball joint
• Front lower arm bushings
• Stabilizer and control links
• Wheel hubs and bearings
• Rear suspension arms and bushings
• Disc plate
7
Vehicle lean
• Wheels and tires
• Vehicle load
• Suspension components
• Incorrect ride height
8
Poor steering return
• High knuckle rotating torque
• Power steering fluid level
• Wheel alignment
9

No. 1 Drift Left or Right

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT TIRES FOR EXCESSIVE WEAR OR DAMAGE
Are the tires normal?
Yes
Go to the next step.
No
Replace the tires.
2
INSPECT STEERING GEAR AND LINKAGE
Lift up the vehicle.
Inspect the steering system for excessive wear and damage.
Is the steering system normal?
Yes
Go to the next step.
No
Repair or replace steering components, as necessary.
3
INSPECT WHEEL ALIGNMENT
Is the wheel alignment within specification?
Yes
Go to the next step.
No
Adjust the wheel alignment.
4
INSPECT FOR BRAKE DRAG
Apply the brakes while driving.
Does drift or pull occur when the brakes are applied?
Yes
Refer to steering system diagnosis/testing, and perform diagnosis.
No
If the steering wheel remains centered, the vehicle is normal.
If the steering wheel is off-center, go to "No. 2 Steering wheel off-center".

No. 2 Steering Wheel Off-center

Diagnostic procedure

STEP

INSPECTION

ACTION

1
VISUALLY INSPECT STEERING WHEEL DEVIATION
Is the steering wheel deviation within the specification.
Yes
Go to the next step.
No
Adjust the steering wheel deviation to specification.
2
INSPECT STEERING GEAR AND LINKAGE
Lift up the vehicle.
Inspect the steering system for wear and damage.
Is the steering system normal?
Yes
If the vehicle tracks correctly, then it is normal.
If the vehicle does not track correctly, go to "No. 3 Tracks incorrectly".
No
Repair or replace steering components, as necessary.

No. 3 Tracks Incorrectly

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT CASTER
Is the caster within specification?
Yes
Go to the next step.
No
Adjust the caster and camber.
2
INSPECT REAR SUSPENSION
Measure the LH and RH wheel base.
Compare the measurements.
Are the measurements the same?
Yes
If the ride is smooth, the vehicle is normal.
If the ride is not smooth, go to "No. 4 Rough ride".
No
Repair or replace rear suspension components, as necessary.

No. 4 Rough Ride

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT FRONT SHOCK ABSORBERS FOR OIL LEAKAGE OR DAMAGE
Lift up the vehicle.
Do the front shock absorbers have oil leakage?
Yes
Replace the front shock absorbers.
No
Go to the next step.
2
INSPECT REAR SHOCK ABSORBERS FOR OIL LEAKAGE OR DAMAGE
Do the rear shock absorbers have oil leakage?
Yes
Replace the rear shock absorbers.
No
Vehicle is normal.

No. 5 Excessive Noise

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT SUSPENSION SYSTEM
Lift up the vehicle.
Inspect the shock absorber installation bolts.
Are the installation bolts loose or damaged?
Yes
Tighten or replace the installation bolts.
No
Go to the next step.
2
INSPECT COIL SPRINGS AND STABILIZERS FOR DAMAGE
Are the coil springs and stabilizers normal?
Yes
Go to the next step.
No
Replace the coil springs or stabilizers.
3
INSPECT FRONT SUSPENSION
Are the front suspension components worn or damaged?
Yes
Replace the front suspension components.
No
Vehicle is normal.

No. 6 Uneven Tire Wear

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT TIRES
Lift up the vehicle.
Inspect the tires for uneven wear on the inner and outer shoulders.
Are the tires normal?
Yes
Go to the next step.
No
Adjust the wheel alignment. If the tires have significant wear, replace them.
2
INSPECT TIRE WEAR
Do the tires have a feathering wear pattern?
Yes
Adjust the wheel alignment. If the tires have significant wear, replace them.
No
Go to the next step.
3
INSPECT TIRES FOR CUPPING OR DISHING
Do the tires have any cupping or dishing?
Yes
Adjust the wheel balance and rotate the tires.
No
Vehicle is normal.

No.7 Vibration

Diagnostic procedure

STEP

INSPECTION

ACTION

1
ROAD TEST
Accelerate the vehicle to the speed at which the customer indicated the vibration occurs.
Is vibration present?
Yes
Go to the next step.
No
This is considered as a concern due to NVH. Identify NVH cause, and repair or replace.
2
INSPECT TIRES
Inspect the tires for unusual wear, cupping, or flat spots.
Are the tires normal?
Yes
Go to the next step.
No
Inspect the suspension components for misalignment, unusual wear, or damage that may have contributed to tire wear.
Repair any malfunction, and adjust or replace the tires.
3
INSPECT WHEEL BEARINGS
Rotate the tires by hand and inspect the wheel bearing play.
Are the wheel bearings normal?
Yes
Go to the next step.
No
Replace wheel bearings, as necessary.
4
INSPECT WHEEL BALANCE
Is wheel balance normal?
Yes
Go to the next step.
No
Adjust wheel balance, as necessary.
5
INSPECT RUNOUT
Perform the following measurements on all wheels.
• high point of the tire and wheel total radial runout
• high point of the wheel radial runout
• high point of the wheel lateral runout
Are the runouts as specified?
Yes
Go to Step 7.
No
Go to the next step.
6
TEMPORARILY INSTALL TIRES AND INSPECT
Temporarily install a set of wheels and tires known to be normal.
Road test the vehicle.
If the vehicle still exhibits shaking or vibration, note the vehicle speed and RPM at which it occurs.
Is vibration present?
Yes
Go to the next step.
No
Install the original wheels and tires one by one, road testing at each step until the damaged tire is identified.
Replace tires and wheels, as necessary.
7
DIAGNOSE WHETHER CAUSE OF PROBLEM IS IN ENGINE/TRANSAXLE OR DRIVE SHAFT/SUSPENSION
Rotate each of the four wheels independently to identify the location generating the vibration.
For the rear wheels, use an on-car balance machine.(2WD)
For the front wheels, accelerate to half the critical speed (vibration occurred) observed in the road test.
Is vibration present in the wheels?
Yes
This is considered as a concern due to NVH. Identify NVH cause, and repair or replace.
No
Perform diagnosis of the engine and ATX.

No. 8 Vehicle Leans

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT TIRE PRESSURE
Is tire inflation normal?
Yes
Go to the next step.
No
Adjust tire inflation.
2
INSPECT VEHICLE LOAD
Is load condition normal?
Yes
Go to the next step.
No
Adjust load volume, as necessary.
3
VISUALLY INSPECT SUSPENSION SYSTEM
Is the suspension system normal?
Yes
Go to the next step.
No
Repair or replace suspension components, as necessary.
4
INSPECT VEHICLE HEIGHT
Is vehicle height normal?
Yes
Vehicle is normal.
No
Adjust vehicle height, as necessary.

No. 9 Poor Steering Return

Diagnostic procedure

STEP

INSPECTION

ACTION

1
INSPECT TIE-ROD ENDS AND LOWER ARM BALL JOINTS FOR STICKING
Are the tie-rod ends and lower arm ball joints free of sticking?
Yes
Go to the next step.
No
Repair or replace component parts as necessary.
2
INSPECT POWER STEERING FLUID LEVEL
Is the power steering fluid level normal?
Yes
Go to the next step.
No
Correct the power steering fluid level.
3
INSPECT WHEEL ALIGNMENT
Is the wheel alignment within the specification?
Yes
Vehicle is normal.
No
Adjust the wheel alignment.