A few days ago, I replaced the short return hose between the power steering oil cooler and the reservoir. Doing so got air into the pump, as would be expected.

My first attempt at purging was to lift the front of the vehicle, run the engine at idle and turn the steering from one side to the other several times. This did not seem to purge any air from the system, but rather made the fluid in the reservior resemble a nice froth.

I drove it in this state for one day. Here's a suggestion: don't do it. The power steering was very bad, to the point that it would take a second or so to apply pressure when there was resistance at the wheels. Parking lots were no fun. Also, the air in the rack seemed to affect the damping, and there was a nice shimmy at about 55 mph which went away at higher speeds.

When it was in this state, the pump groaned loudly when any pressure was applied to the rack. You could hear it inside the car, and feel it vibrating the body.

My second attempt was that night. I let the car sit for a few hours and again raised the front, but this time turned the steering wheel from one side to the other a few times first. I heard the noise of air moving through fluid, so I checked the reservoir, and was happy to see that the level had dropped about a half an inch. So I topped off the reservoir and turned it some more, with the engine off. Then I started the engine and turned yet some more.

The power steering now feels like it should, so apparantly my purging technique worked well enough. But how are you supposed to do it?