Hinges on car doors are subject to weathering, vibration and normal wear and tear as the doors are opened and closed hundreds of times over the lifespan of a vehicle. In addition, gravitational effects pull downward on the doors as they are opened, and, after an unspecified number of open-close cycles, the bolt holes and the pins in the hinges become worn. As they wear, it becomes necessary to either replace the door hinges or, at the very least, place shims in the hinges as a temporary measure for getting the door to open and close properly until a more permanent repair can be made.
Open the car door and, using a proper socket and wrench, remove the far bottom hinge bolt. Close the tips of a set of measuring calipers onto the thread end of the bolt to determine the inside diameter of the washers you will need for the bolt.
Replace the bottom bolt in the hinge and screw down just until the bolt head comes to rest against the surface of the hinge.
Open the car door as far as it will go. Place two hydraulic floor jacks under the car door, one nearest the hinges and the other near the end containing the door handle. Place a 4-foot 2-by-4 board across the tops of the two jacks and place a carpenter's bubble level in the centre. Adjust either one of the jacks until the board is levelled.
Slowly raise the board up against the underside of the car door, just until the board begins to touch the surface of the door on the end which is sagging. There will be a gap between the board on the hinged end of the door nearest the hinges. Keep the board level by pulling each jack handle one time, alternating back and forth between the jacks.
Loosen all hinge bolts by no more than one-half turn. Pump the handle of the jack nearest to the hinges a half pump, and then pump the handle of the further jack one full pump. Remove the bottom two bolts from the bottom door hinge and loosen the top bolt 3 to 4 turns so the hinge pulls away slightly from the frame.
Place washers between the rear side of the hinge and the door frame and slide the bolts through the hinges and the washers, continuing to screw them into the frame. Use one washer on the middle bolt and two washers on the lower bolt. In doing so, you are providing a "shim" which raises the rear of the door by approximately 3/8 inch.
Lower the jacks away from the bottom of the door and screw in the hinge bolts tightly. Slowly and carefully close and open the door several times to test operation of the door. If the door continues to sag, repeat steps 3 through 6, adding only one washer to the bottom hinge bolt and tighten. Test the door once again for proper operation.
If your door isn't properly adjusted after the addition of one washer on the centre bolt of the bottom hinge and three washers on the far bottom bolt of the bottom hinge maximum, it is recommended to take your car to a certified auto-body centre for further repairs, because such repairs are beyond the scope of most do-it-yourself techniques. If you can't get washers, use door alignment shims.
Never remove the bolts from both top and bottom hinges while supporting only the bottom of the door, as the door may fall. If you find it necessary to remove the bolts from both hinges for any reason, have a partner to assist in stabilising the door. Do not over-tighten the hinge bolts. Stripped hinge bolts will vibrate loose making any adjustments you made completely irrelevant. Any temporary door adjustment using shimming techniques should always be considered short-term, with emphasis on the word "temporary." The non-shimmed hinge will experience additional stress, which may accelerate wear to the other hinge as well. Have your car door professionally aligned as soon as possible.