Ok, I finished all the primary mechanical work on a new to me 850 Turbo Wagon - timing belt, water pump and rollers, serpentine belt, drive axles, control arms, lower and upper engine mounts. The last thing I am working thru is heavy steering. The u-joint is not binding since it is smooth and free with the wheels off the ground. I replaced the PS fluid withe Mobil syn AT fluid. There are no obvious leaks anywhere in the system. With the engine running and the PS pump cap off I don't see much fluid movement. When I have someone else turn the wheel in either direction the pump makes noise and vibrates/shutters significantly. Is this likely a bad pump and not the rack? Should I not see a lot of fluid movement with the cap off?

How many miles on the car? It might be due for a new pump. Good news is they are a lot cheaper and easier to replace than a rack...:)

Has the car sat for any length of time?

If so, could simply be that the pump is running very rough from lack of use. No lubrication etc. My 95 855 recently sat for awhile and I noticed the PS pump was loud and noisy. Once the car was used on a regular basis again the noise decreased.

You mentioned just changing over to synthetic PS. With time, the synthetic might also help lubricate the pump.

I've never tried this, but you could add some (Lucas or other brand) PS pump additive to the fluid. Be sure and remove the same amount of fluid so as not to overfill. I wouldn't condemn the pump too quickly. They are pretty robust in those cars. Time and improved lubrication might cure it.

Oh yeah, one last thought. Check the condition of the low pressure hose to the pump. I've seen them go on V70's. And it may not be due to a leak. It is quite a long shot, but if the hose is original it could be breaking down inside and causing a fluid clog.

The car has close to 200k. The noise is not a whining sound normally associated with a bad pump or one low on fluid. The noise only happens when I turn. I will.check the return line, in fact I may just diconnect and see how much fluid it is moving.

My car also made more noise when turning the wheel. It was pretty quiet otherwise. Strangely enough it was worse when turning towards one side than the other (toward driver's side). With use the noise may go away.

Ok drained the reservoir and watched briefly while the engine was running saw the fluid get pumped back into the reservoir so I know the pump is moving fluid and there aren't any significant blockages. Obviously I don't know what kind of pressure the pump is building. However I tried racing the engine to about 2K rpm while in park and then turning the steering wheel to see if the extra output of the pump would reduce the turning effort. It certainly made more noise but the effort was almost normal and quite easy. I don't know if I can draw any certain conclusions except at least at that pump output the rack was operating close to normal. I'm starting to lean more towards the pump and not the rack. Anybody care to weigh in?