Is it normal to have bubbles in the header tank of the power steering reservoir? When the car sits over night, the oil is clean and dark, but when starting the engine bubbles appear in the header tank. When switching the car off, the oil is aerated with fine bubbles, and looks lighter in colour. Putting a screwdriver into the oil, one can fine bubbles on the stem. I’m still chasing a wheel wobble problem, and was wondering if this could cause the problem.
Before starting the engine : -

While engine is running : -


Any help would be great.

Thanks
John