1999 Ford Windstar Repair Question
If it stops turning when you hold the steering wheel, the spool valve is sticking. Also check for any play or looseness in the u-joints in the steering column. That looseness won't CAUSE that problem but can exaggerate it until the valve frees up. That might clear up on its own as it wears a little. If you have to really tug on the steering wheel to get it to stop moving on its own, there is something wrong with the spool valve or its installation. Warranty will take care of a replacement. Are the two steel line nuts different sizes so there's no chance they are switched?
The two lines are the same size. If they were switched by mistake would that cause the problem?
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I never did that but I would suspect you would have to try pretty hard to mix them up. Normally, when you turn the steering wheel / spool valve, two ports open on the valve. One directs pressurized fluid to one side of the power piston in the rack assembly and forces it to move. That pushes the fluid out from the other side and through the second port back to the reservoir. You turn one part of the spool valve to open the ports. As the rack moves, it turns the second part of the valve to close those ports. That's what makes the power piston stop moving as soon as you stop moving the steering wheel, and that's what isn't happening now. Now that I think of it, if the lines were reversed, the pressurized fluid would go to the wrong side of the power piston through the return port and push the piston the wrong way. The force is extremely strong and there would be no way you could hold the steering wheel to stop it. What you would have to do is turn the steering wheel the opposite direction very quickly to close the valve, and most likely you'd go too far and the rack would take off the other way. (I don't think you have the lines reversed).
I switched the two lines and it solved the problem. The two ports are next to each other and there is plenty of hose on both lines to reach both ports. Not to mention that you can only get one hand in there and it is hard to see what goes where. Thanks for your help.
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Dandy news. I'm going to have to rethink my description of fluid flow. Very happy you solved the problem.