After the car has been driven awhile and warmed up, 30 mins or so. the steering wheel starts to jerk and the car pulls to the left. when this happens the car drives like it's on a flat tire, a kluck kluck kluck sound is coming from the front end, but the tires are not flat. i even replaced the old tires with new ones. the steering becomes very erratic. ive taken it twice to a nissan dealer and a sears auto center, and was told everything was tight in the front end. no one seems to know what the problem is, because they can't get the car to recreate this condition. what would be the likely cause that would make this happen?