Steering: 70: Steering Issues

[Richard N]

I am having recurring steering issues with my 1998 V70R AWD. 55,000 miles.

When I first purchased the car 24 months ago the steering was stiff when moving the wheels lock to lock. This occurred with wheels on the ground and also on a ramp with the wheels free. It is best described as a stick slip vibration / juddering through the steering wheel, as if the rack or some other component of the steering was dry.
I checked all the tie rod ends and all were good and not seized. All other joints were good and the top strut bearings appeared OK. The pump reservoir was at the correct level.
After working the steering lock to lock with wheels off the ground pushing on the wheels, not using the steering wheel, it eased up and has been OK for 9 months, albeit slightly heavy compared to my previous T5R.

Three weeks ago the PS pump started making a whining noise when turning. The pitch rose as the engine revs increased and the noise became noticeably louder and the steering heavier over a two week period. With the car stationary and moving the steering slightly to left or right the noise was as if the pump was at hard lock and labouring. There are no leaks in the system.

I replaced the PS pump with a new one thinking it was at fault. The wining when turning is much less but still occurs intermittently on hard lock.
Another issue has arisen in that if I try to turn the wheel quickly the steering becomes very stiff / lumpy and almost locks up. Its OK on slow turns.

When changing the pump the fluid was reddish brown / black. I read in another post that the steering pipes can corrode and create swarf which blocks filters and pumps especially with old fluid.

Is it possible that something is blocking the rack internally?
Any suggestions before I start replacing strut bearings and steering rack?