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Rack & Pinion Steering Replacement
2007 PT Cruiser
Rack & pinion steering became the conventional steering design more than 25 years ago, replacing the recirculating ball design. The rack & pinion design is more precise in function and more compact in size. Most designs use hydraulic fluid to operate the steering gear, but in recent years, the use of an electric motor has replaced the fluid. The ease of servicing components and the entire assembly varies from vehicle to vehicle, depending mostly on access due to the particular vehicle design.
Fundamentals of Rack & Pinion Steering
The operating principle of a rack & pinion steering gear, mechanically, is quite simple. When the driver turns the steering wheel, the rotational motion is converted into linear (side-to-side) motion through the meshing of the helical pinion gear on the steering column with the rack teeth on the steering gear. The lateral movement pushes and pulls the outer tie rod ends to change the direction of the front wheels to steer the vehicle.
Hydraulic power assist is provided by pressurized fluid that moves the rack gear side to side. This is the result of the fluid being diverted to either side of a piston installed on the rack gear. Pressure diverted to the right side of the rack gear piston moves the rack gear to the left, steering the vehicle to the right. Pressure diverted to the left side of the rack gear piston moves the rack gear to the right, steering the vehicle to the left. The flow of the pressurized fluid is controlled by a spool valve on the input shaft. The mechanical movement of the pinion gear provides very little effort in steering the vehicle, but enables it to be steered if power assist is lost.
On many late model vehicles, including the Dodge Dart, Chrysler 200, Chrysler 300 and Dodge Challenger/Charger, electric power steering (EPS) is available. With this design, an electric motor is utilized to move the rack gear side to side to steer the vehicle. This is a simplified power assist design as the hydraulic pump, pressurized fluid and hydraulic lines and hoses have been eliminated. As with the hydraulic design, mechanical steering is available if the power assist is lost.
2007 PT Cruiser
The 2007 PT Cruiser is the subject vehicle for this article and it was only available with hydraulic power assist. The power steering system consists of the following components:
✔ Power steering pump
✔ Power steering rack & pinion gear
✔ Power steering fluid reservoir
✔ Power steering fluid pressure/return hoses
✔ Power steering fluid cooler
The major components of the power rack & pinion steering gear are the outer tie rod ends, inner tie rod ends and protective boots. All of these components are serviceable.
Diagnosing Power Steering Problems
Problems with the power assist on a rack & pinion steering gear are usually easily noticeable by the driver. Generally, it is an increase in effort needed to steer the car. There are several reasons why it becomes difficult, the most common being an external steering fluid leak, or an internal steering fluid leak. In both cases, there is a decrease in the amount of fluid available for power assist.
An external leak is easy to notice as the fluid will be seen on the ground under the vehicle. An internal leak is a bit trickier to find. The net effect, though, is the same. An external leak can usually be traced to a damaged fluid line or bad hose connector. These problems are easily fixed. If an internal leak is suspected, hydraulic flow and pressure test should be performed.
The hydraulic flow and pressure test will verify the performance of the power steering pump and determine if the steering gear is leaking internally. Let’s assume the power steering pump is good. Using the power steering analyzer flow meter, completely open the valve. Turn the steering wheel to the extreme left until the gear hits the stop. Record the pressure. Turn the steering wheel to the extreme right until the gear hits the stop. Record the pressure. Compare the readings to the specs. If the highest output pressure reading against one stop is not within 50 psi of the highest reading at the other stop, the steering gear is leaking internally. The steering gear must be replaced.
If the steering gear is noisy (objectionable hiss or whistle sound), this could be an indication of a bad steering gear. To verify this problem, a simple test can be performed. Check and adjust the power steering fluid, as necessary. Start the vehicle and heat the steering system by rotating the steering wheel lock to lock five times with the engine running at 3000 rpm (don’t hold the steering gear against the stops for more than 15 seconds at a time). Center the steering wheel and return the engine speed to idle. Slowly turn the wheel off center during a dry park maneuver while listening for the noise. If the hissing or whistling sound is present, the steering gear is bad and must be replaced.
Replacing the Rack & Pinion Steering Gear
Replacing the steering gear can be a time consuming job on the PT Cruiser due to space constraints on this front-wheel drive car. Let’s review this procedure in a step-by-step fashion.
1. ›› Lock the steering wheel in the straight ahead position; this keeps the clockspring in the proper orientation.
2. ›› At the base of the steering column, remove the pinch bolt and separate steering column coupling.
3. ›› Raise the vehicle, secure it on jackstands and remove both front wheels.
4. ›› On each side of the vehicle, separate the outer tie rod end from the steering knuckle (Figure 1).
5. ›› Disconnect the wiring harness connector for the power steering fluid pressure switch.
6. ›› On nonturbo cars, remove the pressure hose at the steering gear, then remove the cooler hose at the steering gear outlet port fitting.
7. ›› On turbocars, remove the pressure hose at the steering gear, then remove the return hose at the steering gear outlet port fitting.
8. ›› Remove the two screws that secure the cooler to the suspension crossmember; allow the cooler to hang out of the way.
9. ›› Remove the pencil strut from the right corner of the crossmember and body.
10. ›› Remove one fastener that secures the wheel house splash shield to the drive belt splash shield, then remove the fastener that secures the drive belt splash shield to the front crossmember.
Note: It might be necessary to remove some of the fasteners that secure the front fascia to the body lower reinforcement in order to access the drive belt splash shield forward fastener.
11. ›› Remove the drive belt splash shield.
12. ›› Remove the bolt that mounts the engine torque strut to the crossmember.
13. ›› Mark the position of the front crossmember on the body; this is critical to preserve the preset camber and caster settings (Figure 2).
14. ›› Lower the front crossmember using a transmission jack to access the lower steering column coupling.
Note: Lower the steering gear slowly, being careful not to overextend or damage the fluid hoses.
15. ›› Separate the lower coupling from the steering gear input shaft, then remove the pinion shaft dash cover seal.
16. ›› Remove the steering gear from the front crossmember (Figure 3).
To install the new steering gear, follow the removal steps in the reverse order. Be sure to properly align the crossmember with the scribed mark as noted in Step 13.
For more step-by-step repair instructions, visit www.techauthority.com.