I noticed when in park with the car running when turning the steering wheel the tires appear to shake back and forth. I would compare this movement to a pager on vibrate. I also noticed when driving and turning a corner this motion does not occur. I replaced the return and pressure power steering lines because there was a hole in one of them...originally I thought the shaking of the tires was related to air in the lines. After replacing the lines and putting in power steering fluid I turned the steering wheel back and forth to remove the air from the lines....the shaking of the tires got better as we turned the steering wheel. My neighbor said the shaking would go away as the air was removed from the lines. However, I noticed today that the shaking has not gone away completely(the lines were replaced about 2 weeks ago). I thougth this might be an alignment problem but when driving, the car does not pull to one side or the other. Can anyone help me? Have any ideas?