Steering System-General Information: Other Ford Thunderbird XI

Material

MATERIAL CHART

Variable Assist Power Steering (VAPS)

The VAPS system controls the level of power assistance available to the driver based on vehicle speed. Below 3.2 km/h (2 mph), full power steering assist is provided to lessen steering efforts and increase maneuverability. Between 3.2 km/h (2 mph) and 191 km/h (119 mph), steering assist will decrease gradually at a calibrated rate to raise steering efforts for increased directional stability and greater road feel. Above 191 km/h (119 mph), steering assist is constant.

The front electronic module (FEM) outputs a pulse-width-modulated (PWM) current to the control valve actuator. The control valve actuator controls the hydraulic valve that determines the amount of hydraulic assist provided to the steering gear. The amount of assistance provided varies with the control valve actuator current, which is based on vehicle speed according to a look-up table internal to the FEM. The FEM pulsewidth modulates the control valve actuator current to provide the desired amount of assistance. The amount of hydraulic steering assistance provided by the VAPS subsystem is proportional to the average control valve current.

The vehicle speed is provided to the FEM through the standard corporate protocol (SCP) network from the anti-lock brake system (ABS).

The engine rpm is provided to the FEM through the SCP network from the powertrain control module (PCM). The FEM uses the engine rpm to determine if the engine is running. The FEM will only output control valve actuator current when the engine is running to minimize noise, vibration, or harshness when the engine is off. The FEM will assume the engine is running only if the engine rpm is greater than 100 rpm.

Upon engine start, the FEM will provide a 200 millisecond full-on pulse followed by a 150 millisecond full-off pulse to the control valve actuator. Normal VAPS system operation will begin after this cleaning stroke is complete. In an event that the rpm signal is invalid from the PCM (less than 100 rpm), and the vehicle speed is less than 1.6 km/h (1 mph), the VAPS system will not carry out the cleaning stroke or apply current to the control valve actuator. When the engine speed exceeds 100 rpm, the system carries out the cleaning stroke and begins applying calibrated current to the actuator.

Scheme 14

1. Verify the customer concern.
2. Visually inspect for obvious signs of mechanical damage. VISUAL INSPECTION CHART Mechanical Electrical Fluid level Tire pressure Tires Drive belt Drive belt tensioner Steering column alignment Tie rod ends Suspension components Steering column shaft U-joints Intermediate shaft bolts Power steering reservoir baffle Power steering reservoir filter Power steering pressure lines, fittings or O-rings Power steering return hoses and clamps Steering gear Power steering pump Wiring Connectors
3. Inspect the power steering fluid for the following conditions: Aerated or foamy: Purge the power steering system. Refer to «POWER STEERING SYSTEM PURGING»(ref-204554-S13063724752005111200000) . Overheating or contamination: Flush the power steering system. Refer to «POWER STEERING SYSTEM FILLING»(ref-204554-S25224036172005111200000) .
4. Check the power steering system for fluid leaks. Check the power steering fluid level. NOTE: It may be necessary to add power steering fluid to achieve the correct level. With the ignition OFF: Wipe off the power steering pump, power steering pressure hose, power steering return hose, power steering fluid cooler, hose assembly and steering gear. CAUTION: Do not hold the steering wheel at the stops for an extended amount of time. Damage to the power steering pump can occur. Start the engine and turn the steering wheel from stop-to-stop several times and check for leaks. If a fluid leak from the steering line-to-steering gear clamp plate is evident, refer to «POWER STEERING»(ref-204555) .
5. Inspect the power steering pressure and return hoses, fittings and O-rings for leaks. If a leak is detected at a power steering pressure or return hose, install a new hose. Refer to «POWER STEERING»(ref-204555) . If a leak is detected between a fitting nut, seal the fitting nut using a Teflon(R) joint seal. If a leak is detected at a fitting or clamp plate, tighten to specification. If leak is still evident, visually inspect the fittings, clamp plate, O-rings, and Teflonr seals. Install new as necessary. Refer to «POWER STEERING»(ref-204555) . If a leak is detected at the power steering reservoir, install a new reservoir. Refer to «POWER STEERING»(ref-204555) . If a leak is detected at a constant tension spring clamp, verify that the hose is fully installed on the fitting and that the hose clamp is correctly positioned. If the leak remains, install a new screw clamp. If a leak is detected at a screw clamp joint, tighten the screw clamp. If the leak remains, inspect the tube end and install a new hose. Refer to «POWER STEERING»(ref-204555) . If a leak is detected at the power steering pump, install a new power steering pump. Refer to «POWER STEERING»(ref-204555) . NOTE: To inspect for leaks it may be necessary to remove the squeeze-type clamp from the steering gear boots.
6. Inspect the power steering gear for leaks. If a leak is detected at the power steering gear, install a new power steering gear. Refer to «POWER STEERING»(ref-204555) .
7. If an obvious cause for an observed or reported concern is found, correct the cause before proceeding to the next step.
8. If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC) located beneath the instrument panel, and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle: Check that the program card is correctly installed. Check the connections to the vehicle. Check the ignition switch position.
9. If the diagnostic tool still does not communicate with the vehicle, refer to the tester manual.
10. Carry out the diagnostic tool data link test. If the diagnostic tool responds with: SCP or ISO; all electronic control units no response/not equipped, refer to «MODULE COMMUNICATIONS NETWORK»(ref-204591) . No response/not equipped for FEM, refer to «MODULE COMMUNICATIONS NETWORK»(ref-204591) . System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out the self-test diagnostics for the FEM.
11. If the DTCs retrieved are related to the concern, go to the «FRONT ELECTRONIC MODULE (FEM) DIAGNOSTIC TROUBLE CODE (DTC) INDEX»(ref-204554-S35160516462005111200000) to continue diagnostics.
12. If no DTCs related to the concern are retrieved, proceed to next step to continue diagnostics.
13. If an obvious cause for an observed or reported concern is found, correct the cause before proceeding to the next step.
14. If the cause is not visually evident, verify the symptom and GO to «SYMPTOM CHART»(ref-204554-S39651083182005111200000)

Drift/Pull

Pull is described as a tugging sensation, felt by the hands on the steering wheel, that must be overcome to keep the vehicle going straight.

Drift describes what a vehicle with this condition does with the hands off the steering wheel.

1. A vehicle-related drift/pull, on a flat road, can cause a consistent deviation from the straight-ahead path and require constant steering input in the opposite direction to counteract the effect.
2. Drift/pull can be induced by conditions external to the vehicle (i.e., wind, road camber).

Excessive Steering Wheel Play

Excessive steering wheel play is a condition in which there is too much steering wheel movement before the wheels move. A small amount of steering wheel free play is considered normal.

Feedback

Feedback is a roughness felt in the steering wheel when the vehicle is driven over rough pavement.

Hard Steering or Lack of Assist

Hard steering or lack of assist is experienced when the steering wheel effort exceeds specifications. Hard steering can remain constant through the full turn or occur near the end of a turn. It is important to know the difference between hard steering/lack of assist and binding.

Hard steering or lack of assist can result from either hydraulic or mechanical conditions. It is extremely important to know if this concern occurs during driving or during high-effort parking maneuvers.

Nibble

Sometimes confused with shimmy, nibble is a condition resulting from tire interaction with various road surfaces and observed by the driver as small rotational oscillations of the steering wheel.

Poor Returnability/Sticky Steering

Poor returnability and sticky steering is used to describe the poor return of the steering wheel to center after a turn, or the steering correction, is completed.

Shimmy

Shimmy, as observed by the driver, is large, consistent, rotational oscillations of the steering wheel resulting from large, side-to-side (lateral) tire/wheel movements.

Shimmy is usually experienced near 64 km/h (40 mph), and can begin or be amplified when the tire contacts pot holes or irregularities in the road surface.

Wander

Wander is the tendency of the vehicle to require frequent, random left and right steering wheel corrections to maintain a straight path down a level road.

Steering Linkage

1. With the vehicle on the ground and the parking brake applied, carry out the following: Have an assistant rotate the steering wheel back and forth 360 degrees and watch for relative motion of the studs in the steering linkage ball sockets. Watch for a loose steering gear mounting.
2. An additional check is with the KOEO and the front wheels raised off the ground, grasp the wheel at the front and rear and watch for excessive play or binding in the joints while trying to steer the wheels.
3. Joints can be checked for excessive wear by measuring the torque it takes t turn the stud. Separate the tapered stud from its seat and thread the attaching nut back onto the stud. NOTE: Some joint turning torques will be as little as 0.2 N.m (2.0 lb-in) within the first 1,600 km (1,000 miles) and will remain there for the life of the joint. Turn the stud with an inch-pound torque wrench and note the torque required to turn the stud. TORQUE SPECIFICATION Torque Required to Turn Stud in Socket N.m Lb-In New joints 2.0-5.0 18.0-47.0 Used joints 0.2-3.0 2.0-26.0 Joints with excessive play Less than 0.2 Less than 2.0
4. Install new components if necessary. Tighten any worn, damaged, or loose components.

Steering Gear Valve

1. With the vehicle in motion, place the transmission in NEUTRAL and turn the engine OFF. If the vehicle does not pull with the engine OFF, repair or install a new steering gear. Refer to «POWER STEERING»(ref-204555) .
2. If the vehicle pulls with the engine OFF, switch the right side front wheel to the left side of the vehicle and the left side front wheel to the right side of the vehicle.
3. If the vehicle pulls to the opposite side, switch the front wheels with the rear wheels keeping them on the same side of the vehicle.
4. If the vehicle pull direction does not change, check the front suspension components, wheel alignment and frame alignment. Refer to «DESCRIPTION AND OPERATION»(ref-169465-S24833207802004120900000) in Front in Suspension or «DESCRIPTION AND OPERATION»(ref-169787-S08275400402004121500000) in Rear in Suspension.

MATERIAL CHART

1. Remove the power steering fluid reservoir cap.
2. Using a suitable suction device, remove the power steering fluid from the reservoir.
3. Disconnect the power steering fluid return hose from the reservoir. Remove the clamp.
4. Plug the power steering fluid reservoir inlet port.
5. Attach an extension hose to the power steering return hose.
6. Place the open end of the extension hose into a suitable container.
7. Fill the power steering fluid reservoir with new fluid.
8. Start the engine while simultaneously turning the steering wheel to lock and then immediately turn the ignition switch to the OFF position.
9. Fill the power steering fluid reservoir with the approved power steering fluid.
10. Repeat Steps 8 and 9, turning the steering wheel in the opposite direction each time, until the fluid exiting the power steering fluid return hose is clean and clear of foreign material.
11. Remove the extension hose from the power steering return hose.
12. Remove the plug from the power steering fluid reservoir inlet port.
13. Install the power steering return hose to the reservoir. Install the clamp.
14. If, after properly filling the power steering system, there is power steering noise accompanied by evidence of aerated fluid and there are no fluid leaks, it may be necessary to purge the power steering system. For additional information, refer to «POWER STEERING SYSTEM PURGING»(ref-204554-S13063724752005111200000) . Fill the power steering system. For additional information, refer to «POWER STEERING SYSTEM FILLING»(ref-204554-S25224036172005111200000) .

Scheme 15

MATERIAL CHART

1. Remove the power steering pump reservoir cap. Check the fluid.
2. Raise the front wheels off the floor. Refer to «JACKING & HOISTING»(ref-232595-S06496072622006051700000) for the procedure.
3. Tightly insert the stopper of the vacuum pump into the reservoir.
4. Start the engine.
5. Install the vacuum pump, apply vacuum, and maintain the maximum vacuum of 68-85 kPa (20-25 in-Hg).
6. If equipped with Hydro-Boost(R), apply the brake pedal twice.
7. Cycle the steering wheel fully from stop-to-stop 10 times.
8. Stop the engine.
9. Release the vacuum and remove the vacuum pump.
10. Fill the reservoir. Use approved transmission fluid.
11. Start the engine.
12. Install the vacuum pump. Apply and maintain the maximum vacuum of 68-85 kPa (20-25 in-Hg).
13. Cycle the steering wheel fully from stop-to-stop 10 times.
14. Stop the engine, release the vacuum and remove the vacuum pump.
15. Fill the reservoir as needed and install the reservoir cap.
16. Visually inspect the power steering system for leaks.
17. Fill the reservoir as needed and visually inspect the power steering system for leaks.
18. Install the reservoir cap.

Scheme 16

MATERIAL CHART

1. Remove the power steering pump reservoir cap.
2. Tightly install the evacuation cap to the power steering pump reservoir.
3. Install the hose from the fill adapter manifold tee to the evacuation cap on the power steering pump reservoir.
4. Install the vacuum pump to the fill adapter manifold control valve.
5. Install the hose to the opposite fill adapter manifold control valve and submerge the open end of the hose into a container of new power steering fluid.
6. Close the fill adapter manifold control valve connected to the power steering fluid container.
7. Open the fill adapter manifold control valve connected to the vacuum pump.
8. Using the vacuum pump, apply 68-85 kPa (20-25 in-Hg) of vacuum to the power steering system.
9. Observe the vacuum gauge for 30 seconds.
10. If the vacuum gauge reading drops more than 3 kPa (0.88 in-Hg), correct any leaks in the power steering system or the filling tools before proceeding.
11. Slowly open the fill adapter manifold control valve connected to the power steering fluid container until power steering fluid completely fills the hose.
12. Close the fill adapter manifold control valve connected to the power steering fluid container.
13. Using the vacuum pump, apply 68-85 kPa (20-25 in-Hg) of vacuum to the power steering system.
14. Close the fill adapter manifold control valve connected to the vacuum pump.
15. Slowly open the fill adapter manifold control valve connected to the power steering fluid container.
16. When the power steering fluid has drained from the hose connected to the power steering fluid container, close the fill adapter manifold control valve connected to the power steering fluid container.
17. Remove the tools from the vehicle.
18. Install the power steering reservoir cap.
19. Start the engine and turn the steering wheel from stop-to-stop.
20. If equipped with Hydro-Boost(R), apply the brake pedal twice.
21. Turn the ignition switch to the OFF position.
22. Remove the power steering reservoir cap and fill the reservoir.
23. Install the power steering reservoir cap.