| Diagnosis and Testing Principles of Operation The steering wheel rotational movement is transferred to the steering gear through the steering column shaft. The steering gear converts this rotational movement, through the action of the rack and pinion gear into lateral movement. This movement in turn is transferred to the wheel knuckles through the tie-rods and tie-rod ends. Hydraulic fluid under pressure is supplied to the steering gear by the power steering pump. As the steering wheel is rotated, the hydraulic fluid is allowed to pass through the steering gear valve to one side of a double acting piston, dependent on which direction the steering wheel is rotated. The fluid moves the piston, which forms part of the steering gear, giving power assistance to the effort required to rotate the steering wheel. Petrol/gasoline engine variants, due to the extra load on the engine imposed by the power steering pump, have a power steering pressure (PSP) switch. The switch, which is normally closed, sends a signal to the powertrain control module (PCM) during low speed parking manoeuvres. The PCM responds by maintaining the engine idle speed. Inspection and Verification - Verify the customer concern.
- Visually inspect for obvious signs of mechanical or electrical damage.
Visual Inspection Chart | Mechanical | Electrical | - Tire pressure
- Accessory drive belt
- Wheels and tires
- Power steering line fluid leaks
| - Power steering pressure (PSP) switch
| - If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
- If the cause is not visually evident, verify the symptom and refer to the Symptom Chart.
Symptom Chart Symptom Chart | Symptom | Possible Sources | Action | | Steering is very difficult/very easy | * Loose or worn accessory drive belt. | * | | * Power steering hose restrictions. | * CHECK the hoses for damage, kinks or restrictions. INSTALL new components as necessary. REFER to Section 211-02 Power Steering. | | * Fluid contamination. | * | | * Fluid aeration. | * | | * Seized suspension ball joints. | * | | * Worn steering gear. | * | | * Worn steering column. | * REFER to Steering Linkage Component Test. | | * Worn power steering pump. | * | | Steering does not vary with increased wheel rotation | * Worn tie-rod ends. | * | | * Worn front suspension bushings. | * | | * Worn suspension ball joints. | * | | * Worn strut and spring assembly top mount. | * | | * Steering gear insulator bushing worn or perished. | * | | * Loose steering gear retaining bolts. | * | | * Loose steering column retaining bolts. | * | | * Loose steering column to steering gear pinion retaining bolt. | * | | * Excessive steering gear backlash | * | | Steering assist does not vary with vehicle speed | * PSP switch or circuit. | * For additional information, REFER to WDS. | Component Tests Steering Linkage Inspect the steering gear boots for cuts, deterioration, twisting or distortion. Make sure the boots are secure, install new boots or clamps as necessary. - Park the vehicle on a dry, even surface and apply the parking brake. Place the steering in the straight - ahead position.
- With the engine running, gently turn the steering wheel to the right and left to check free play. Free play is measured at the steering wheel rim and should be within the limits stated in the specifications. If free play exceeds the limit stated the steering linkage or the steering column is worn, or the backlash of the steering gear is excessive.
- With the engine OFF, hold the steering wheel firmly with both hands. Attempt to move the steering wheel up and down and also to the left and right without turning the wheel, to check for steering column bearing wear, steering column shaft joint play and steering wheel or steering column looseness. If free play is detected, check the correct torque of the steering column, coupling shaft and steering wheel retaining bolts. The steering column cannot be repaired, install a new steering column. REFER to Section 211-04 Steering Column.
|
