Power Steering Blues

My 2001 Windstar had a leaking rack & pinion unit. Replace the rack & pinion and the pump with cardone reman units. Cleaned reservoir and flushed lines. Worked great for 3 days then my wife called and said it made a funny squealing noise and the steering wheel locked up. Went to get it and found steering works a little at high RPM. Pump turns fine and makes no noise, can see flow from return in reservoir at idle. Need troubleshooting info. Where is the flow control valve? In the pump or rack? How about check valves in the rack. Can they stick and cause loss of power? I'm guessing the pump is the problem but how can I check pressure to be sure.

Traildog1

Someone with more experience than I will hopefully chime in.
The pressure control valve is in the power steering pump.
Method for measuring the power steering pressure that is outlined in AlldataDIY calls for a "power steering analyzer" to be installed in between the power steering pump output and the steering rack.
It also has a caution that the power steering fluid pressure can be over 1500psi.

The steering rack contains a "rotary hydraulic fluid control valve" which is "integral" to the steering rack.

You should be able to steer the vehicle (with greater effort...but physically possible) with the engine OFF......no power assist.
So if you cannot do this.....then you have something physically wrong with the mechanicals.....not the power assist portion.
Of course, the steering rack can cause this also.....as it is involved in both the mechanical and power assist loop.


Your problem is sounding like something is physically stuck.

Thanks for the info wiswind. The steering does work with more physical effort. Wifes deffinition of "locked up" was that she couldn't turn the wheel while not moving.

I had time last night to jack up the van and look around a little. With the tires off the ground, the effort to turn the steering wheel is the same with engine off or running at idle. It is somewhat easier at higher engine rpm. After oil got hot return flow to reservoir is less. Still suspect pump.