Two problems related to ball joint have been reported for the 1996 Mercury Grand Marquis. The most recently reported issues are listed below.
I own a 1996 Mercury Grand Marquis. The steering in the vehicle began locking up at a certain spot when turning. This would cause me to push the steering wheel into the turn a little harder which unlocked the steering causing me to veer left or right. I took the car several times to different shops. They would lift the car and check the suspension and give it a clean bill of health. The problem persisted and got much worse. I took the car to yet another shop and insisted they take it out and drive it a long distance. The mechanic didn't get out of the parking lot, came back and made me leave the car. He insisted it was a problem with the steering box and this was replaced. I picked up the car on a Friday and on Saturday drove over the mountains. It was a hairy ride, the problem was not fixed and the curvy roads made driving downright dangerous. I took the car to a mechanic at my destination and he inspected the car but this time he disconnected the tie rod ends so he could rotate the wheels with weight on them. One of the ball joints on the drivers side was nearly locked solid. The drivers side ball joints were replaced and that fixed the problem.
While driving the brake lines failed and had to be replaced. The owner came outside and saw the brake fluid on the ground and realized that the brake lines failed. The owner drove the vehicle with no brakes to the dealership and they repaired it. Then the owner realized that the brake lines were rusted. The left rear seat belt was replaced twice. The wiper motor, wiper switch, drivers side mirror switch and rotors were all replaced. The turn signal switch, driver window switch , tail light , catalytic converter were replaced. The consumer was told the ball joints and shocks were bad. The battery was replaced.