My doors sag when they are opened. What is the problem?
Your hinge pins and bushings are worn out and need to be replaced. While any body shop can replace these, it not too difficult to do yourself. The project should take about 1 to 2 hours. The biggest problem is supporting the heavy door while the pin is out of a hinge. To support the door, I made a U shape out of 3 pieces of 2×4 lumber, each 10 long. I mounted two of the pieces on each end of the third piece so there was a 7 gap between the upright pieces. I used screws and pieces of angle iron to be sure it was strong. I drilled a hole in the center of the bottom of the U, and put a long bolt with a large washer through the hole. I removed the saddle from my floor jack, ran the bolt through the hole that held the saddle, and secured the U to the floor jack using a large washer and nut. To protect the door, I glued some old headliner material inside the U. The U fits between the inside of the door, and the trim on the outside of the door, and securely holds the door in place when a hing