What causes a thumping noise when turning wheel to the left on a Windstar Van?

Answer 1

One possible cause can be worn Sway Bar bushings. You can check them by slipping under the front of the vehicle park on a flat surface with the engine off). Grab the Sway Bar using a good amount of force with your hand, wiggle the bar back and forth while looking at the bushings. The bushings are lubricated when new. You may be able to extend their life and get ride of the thumping by checking them by hand ensuring they are still in place and not in jeopardy of slipping out of their brackets. Using a silicone spray, cover the inside of the bushings were they make contact with the Sway Bar. This worked for me and 1 year later after checking them they still seem OK. If this does not work, seek a professional Mechanic, it could be something else seriously worn out.