Money Pit

Got enough air in your tires
What are your kingpins and bearings look like

Maybe you need a new pump or a new gearbox

 

I had an 08 with a similar problem. The u joints on the steering column are not serviceable. You have to replace the lower part that connects to the steering box. These joints are exposed to all the outside elements and do not last forever

Gl

 

Did you replace the filter in the power steering reservoir?

 

Right when I saw Money Pit i knew this was a Volvo forum. Bought my 08 630 in early December of 2014... She's had over 16 grand in repairs. The latest... Oil pressure sensor, cab shocks, and egr valve 2 coolant hose. Going back soon for cab blower motor and the ds mirror switch.... Love my truck but mannnnnn

 

16 grands it's just beginning.
http://www.thetruckersreport.com/tr.../cost-of-ownership-with-a-volvo.297896/page-4
Here you can have advise how to....
Adviser never had one bu he knows.....

 

When the filter is replaced inspect it inside and out for missing material that may have mucked up the system. Someone else has a post about that, search block top right.
Answer Taxi's questions.
Find someone with a pressure- flow meter to test it. Better to pay for a $100 test replace the problem them spend $1000.00's expermenting.
Your other post is is on power steering for those not following.

 

I has similar problem but it was stiff when driving on turns, the steering shaft was seized on the part that slides in and out( its under the rubber boot that bolts to cab) another symptom to this problem I had it was that the steering wheel will tilt but it will to pull up when trying to adjust.

 

There was a recall by Volvo for steering shaft problems.....