What is the best way to treat rust on the lower edge of a door?
All my previous attempts over the years have seen rust erupting in no time through my beautifully (?) repaired bodywork. I can't help wondering if the rust would advance just as fast if untreated.
A bit of work involved if you want to keep the rust away from the lower edge of the doors, take off the door card 7 components, look inside the door skin to the bottom of the door, clean out the drain holes, clean & treat the rust area then apply a lot of grease to the base of the door, an awful lot of work but it pays dividends.
The only sure way is to replace the rotten areas with new metal. You either cut the rust back to good metal and weld in new (difficult with panels so thin and flat) or replace the door with a new or rust-free one. You can often buy new door skins which weld to the old door frame once you've cut rusted skin away. Whatever, it's important to renew the rubber door seal around the window as the old one has perished and is letting water inside the door.
Why do you say it's not worth paying someone to repair? If you bought the car as an investment with the idea of selling it for a profit then it's right to think you won't recoup the cost. But if you want to keep the car for some time then the cost of repair is incidental. People say this when I renew parts on my 26-year old Golf as a matter of course. I've had the car for 23 years and I hope to have it for another 20 so any profit or loss on the eventual sale is completely incidental. I always say it's like decorating your house if you have no intention of moving. Why bother? You'll never recoup the cost when you eventually sell. The point is, you decorate because it's your money that you want to spend on your house and it makes you feel good to do so. Why should anyone tell you "yer 'ouse ain't worf it mate - it ain't worf spending money on"! People seem to think they can give that sort of nonsensical advice when it comes to cars.
If you want to use your money to get your car repaired so that it looks good and makes you feel better Panic button - then do it. Have someone change the door skin or door, rustproof the inside, repaint the exterior and fit a new the rubber seal. It'll look good, you'll feel good and you'll be proud of your car which sounds like a very good and reliable buy. Hang on to it!