Land Rover doors will at some point in their busy lives suffer from at least one, but if you're unlucky, all of the many quircky faults that can occur due to their design. However, many decades of life can be salvaged from Defender doors, if well maintained or repaired, so worry not!
The most common issue is sticky door catches, windows that rattle, drafty and leaking door seals, and locks that you can more or less open with a spoon (to name just a few!). All but some of the faults can be avoided or even cured with simple maintenance or repair. Regular adjustment of door catch's, a generous squirt of maintenance spray on all moving parts (including key locks) and a brush or spray of grease on the hinge's and door strap's work wonders for regular trouble free use. However, in this article I look at the dreaded corrosion (rust, rot, tin worm - the devil has many names) and how to remove it and replace with a good new metal: A basic door frame re-furb usually means complete lower channel replace and maybe a couple of inches of the bottom of the vertical parts of the frame.
First step; door removal, this may not be what the manual says but after removing a lot of Defender doors over the years it works for me. Remove all fittings from inside the door, door handle, window winder, door catch surround and escutcheon sill (the bit around the door lock button) and then carefully prise off the door card (unless you have electrics which should of course be unplugged and made safe: do not attempt this if you are qualified or suitably experienced). Then remove the clevis pin in the door strap. Once removed, push the strap out of the way and shut the door. With the help of a second person then remove the four srew bolts or torque bolts that hold the door hinge to the bulkhead. Finally, open the door from handle end first and lift off and lay down with the inside facing up on a pair of sturdy trestles.
Second step; (involves the use of power tools, so correct protective equipment must be used; goggles, gloves, a welding mask, leather gauntlets, and fire retardant overalls). With a flat ended lever carefully lift up the fold/seam of the door skin away from bottom of frame, taking care not to damage the outside face. Using an angle grinder and a one millimetre thick cutting blade, cut each bottom corner at forty five degrees, all the way through the original weld line. Extreme caution should be taken not to cut through the very soft aluminium door skin! Remove the old corroded bottom channel and clean off any old bonding glue from inside door skin. An old workshop hoover is handy now to make sure there are no bit?s of rust or rubbish that could get trapped between the door skin and the new portion of frame. Now take your previously primered and protected new length of door channel and measure, cut once to the desired length. Lightly tap this into place and adjust accordingly to create a correct fit. Then, with the rest of door frame clamped flat, weld the new section into position (clearly some welding experience or expertise is required here). Allow the work area to cool.
Using a good quality bonding agent, usually bought in cartridge type containers with cut to size nozzles, apply a small bead of bonding solution between the new frame parts and door skin and lightly press together to create a good seal. Using a proper door skin tool, or a big old pair of pliers with jaws covered, carefully fold the door skin edge over the new frame. TIP: don't squeeze too hard or you will mark the outer face of the door skin.
Third step; and final step before re-fitting, is to finish (paint). With nearly all colours available in spray can form from your local motor factor, it's a couple of coats of primer, and allow to dry. Lightly sand with a fine grade sand paper to create a suitable surface for your colour of choice. Once the paint is dry a coating of waxy oily solution inside the door frame wouldn't be a bad idea.
Remember, while the door is off you have a good opportunity to service any of the door fixings (perhaps some nice new hinges or maybe door seals but at least a good spray of lubricant on all the internal door workings).
Final step; re-fitting, um, reverse the fitting process!
Hope that helps and have fun.