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Driving a Power-Assisted Car
Without Operating Hydraulics
The power-assisted steering linkage system, like that found on early Mustangs, Falcon and Fairlanes, was prone to leak and cause problems with age. A lot of people either didn't want to spend the money to properly repair the system, or just thought that they wanted a "manual" steering system because it gave them more of a performance feel.
The Ford shop manual states that it is possible to drive the car without the hydraulics operating, but it is only recommending this be done to get the car to a repair shop or dealership. The car was not meant to be driven this way for an extended period of time.
Most people removed the belt from the power steering pump, or removed the pump altogether. This eliminated the power assist and "simulated" the feel of true manual steering, but it wasn't quite that. A lot of cars were driven many years this way without ever being properly converted to factory-style components.
There are several reason not to drive a power-assisted car without working hydraulics, mainly because it is dangerous and detrimental to the system.
Due to the design of the ball stud area on a power steering car, and the movement it needs to actuate the control valve, there is a considerable amount of "play" in the ball stud area when the hydraulics are not working. This will cause a lot of road wander and a very loose feeling in the steering.
The play in the ball stud will also reduce "road feel" considerably since the ball stud is now spring loaded at each end, and is not solidly connected to the centerlink.
Look at the pictures of the Ball Stud Bushing below. In the picture of the inside of the bushing, notice the little tangs that are sticking up from the bushing surface. There are four of these tangs, and they are only about 1/10" wide and 1/32" high. One of the Ball Stud Seats rests agaonst these tangs. When the system has working hydraulics, the Ball Stud pushes against the Seat, which pushes against the tangs. This causes the hydraulics to move the linkage. When the hydraulics are not operating, then the full force needed to turn the car to the left is placed upon these four small tangs. If they fail, then the Ball Stud will become very loose inside the bushing, causing more steering play and possibly loss of control.
Look at the bushing pictures again. Notice the sides of the bushing where the Ball Stud comes through. These edges wrap around the ball part of the Ball Stud. While there is some spring tension on the seats holding the Ball Stud in place, it is primarily these edges wrapped around the Ball Stud that hold it in place. These areas get very little wear when the system has working hydraulics, but when the power is off, the Ball Stud moves much more and under greater stress. After many miles of driving like this, the wear and tear on the parts can allow the Ball Stud to pop out of the bushing. When this happens, the front wheels of your car are no longer connected to the steering wheel.
With the power cut off from the system, all the parts are put under much more strain and movement than normal. This will cause many of the parts to wear much faster than normal and cause others to be damaged. The longer the car is driven without power, the more damage will occur and the control valve and ball stud area will become harder to rebuild or will be too badly worn to be repaired.
Driving a car with the hydraulics disabled can actually be harder and require more effort to steer than a regular manual steering car. That is because of the extra drag on the system imposed by the power cylinder and the fluid still in the system. The higher ratio of the steering box used in power steering cars can add significant effort to turning and manuevering the car.
It may be safe to drive a car for a short time with the hydraulic assist disabled (if the related parts are in good working condition to begin with), but it can certainly be detrimental to the parts involved and the steering performance of the car to continue to drive under those conditions. If repairs cannot be done in a timely manner, it is best to replace the power steering components with manual steering parts and make the car a properly built and operating manual steering car.