Steering wheel feels weird

[geminiys]

My dad's 2005 XC70 has developed a weird steering wheel behavior. It is more noticeable at speed - freeways rather than city but if one pays attention, the behavior can be detected at slow speed too. Whenever the car is steered to the left, the feel in the steering has a pulsating effect. In details, with little force from an arm the steering wheel is slightly turned to the left and with about 2 seconds interval the counter-force from the car itself is gone making the arm to fall more to the left. The counter force immediately return back making the entire process to feel like a pulse back-and-force between arm and steering wheel. At times when not ready for this behavior will the car to steer in the lane a little. The problem is more pronounced when steering wheel is turned to the left in comparison to right.
The vehicle has new Control Arms with 16,000 miles on it. It also has new tires 8,000 miles on it. The steering pump fluid is good and level is appropriate. I did the search but found no information on the issue or similar one to it. What are you thoughts on the issue? IS the pump going bad or steering rack?

Thank you

[abscate]

It is probably a problem in the rack rather than the pump but could also be a tire or control arm problem.
When these are subtle, you usually have to drive them for a bit before you can find worn parts.

[oragex]

As above, probably not an easy issue to isolate. Just a note, the control arms, in my opinion, must be either Lemforder or original Volvo brands. Most other brands can fail as soon as 6 months. Another note, with such kind of issue, a Volvo dealer will rather suggest replacing several parts for a scary bill, rather than carefully check each component to find the culprit.

I have read about a pulsing in the steering that has been fixed with fresh Pentosin fluid. But also about a similar issue caused by the rack. Just don't rush and replace the rack before anything else has been checked. How recent/brand are the ball joints? Tie rods ends/inner? Maybe a suspension bolt hasn't been properly tightened? Or an reused bolt has stretched.

[geminiys]

Abscate and Oragex. Thank you for your responses. I will check on all suggested points.
Both control arms are from either Mayle or Lemforder. I don't really remember now, as it was 2-3 years ago when I got them and replaced at my friend's body shop. The ball joints were replaced with arms as a single assembly, therefore it makes me believe they are Mayle brand. I just hope it is not the rack, as I doubt it I want to do this on my own without a lift, on a San Francisco Street.

[oragex]

If Meyle control arms and ball joints, I would bring the car to the shop to have these inspected, 3 years would be a long way for this brand.