As I turn the wheel I get no power steering assistance for about the first 5 to 10 degrees. As I turn harder to get it to move the power steering suddenly kicks in and since I'm pushing hard the steering (and the car) then jerks over in that direction until I can react and correct.

This only happens on a cold morning, after about 10 mins of normal driving it starts working fine. I can get it to work sooner by working the wheel back and forth through the dead points while waiting at the lights.

When in for brake change I had the mechanic check the fluid, it looked clean and at correct level.

Is this likely a pump problem? A sensor problem? What should I try changing first?

Its a S40 2004.5 2.4i

 

Your description sure sounds like a pump issue. Just a guess.