I try to avoid buying cars that have spent more than a year of their existence up North trudging through harsh winters. The mix of snow and salt are not a friend to automobile undercarriages. The problem is, when I shop for cars I’m usually shopping for unique cars that are 10 years old or older and I have a specific exterior and interior color combination that I’m looking for, etc. This doesn’t always give me the ability to be picky about where a car has spent its life. When we purchased the Jaguar it was from someone here in Oklahoma but the previous owner lived in Illinois so the car was there for 5 years. I noticed while giving the car my post-purchase once-over that there was quite a bit surface rust on the subframe.
Although the site of rust on your car isn’t ideal it’s usually not something to cause concern unless it has started to corrode away the metal completely and there are large flakes of metal that can be taken off with ease. Surface rust isn’t something, however, that you should just ignore.
With the front of the car up on ramps I was able to get a good look at most of the rust I needed to take care of. With some safety goggles and good lighting I used my drill with a wire brush attachment to go over all of the rusted areas that I could get to. I used a small wire brush to get to the areas that I couldn’t reach with the drill.
Once I had most of the rust cleaned off to my satisfaction I used shop towels with acetone cleaner to wipe down and clean the surface to prepare for treatment. There are many products that are made to treat rust but I always use the Rust-Oleum product becuase it has always done the job for me. I covered similar surface rust on my 300zx 5 years ago with it and there are no signs of the rust trying to make a comeback.
One thing I could have probably done differently is get an old box or something and held it up to help protect other parts of the car from over-spray. If you really wanted to get serious about it you could tape off everything that you don’t want to get paint on. Once you get things treated with the paint not only is the unsightly rust no longer visible but the rusting process is halted so you don’t have to worry about further corrosion weakening your subframe.
I did the same thing to the rear end of the car after backing it up on the ramps. Time usually proves that I didn’t get everything with this first quick pass so I usually take time with each oil change to clean and repaint some areas that I missed before.