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Q I like my Volkswagen Fox and service it meticulously. It’s in good condition, but I’d like to know how to keep the bodywork and underside from starting to rust. David Atkins, Ludlow
Ed says
A s a general preventative, treat all the box sections and pillars of the car at least up to waist level with a quality cavity wax. For a one-off job, buy large aerosols supplied with long extension lances. They’re clean, convenient and do a good job. Treat the seams inside the door frames and spray inside the lower edge of the bonnet and tailgate. Many modern classics are fitted with plastic wheel arch liners and other shields which keep rust out of wings and crevices. They can sometimes trap dirt around the edges, though, so remove them, clear debris and give the hidden areas a squirt of cavity wax.
The underbody is coated with rubberised PVC sealant. This repels stones and helps with sound insulation. If it gets damaged or it peels along an edge, water and corrosion can force their way underneath it. Identify loose patches and scrape away until you get to clean primer. Dry, remove loose rust and touch in with a primer or all-in-one metal paint. If you notice rust stains and bulges in the coating, investigate: rust may be forcing its way through from a seam or box section. A small welded repair might be necessary. Don’t worry too much about light rust on suspension parts, – but look out for crusty brake pipes. Take the trouble to examine pipes hidden under plastic undertrays. Coat the whole underside, including inside the chassis rails and strengthening members with a quality underbody wax. Don’t use underseal, rubberised coatings, etc, which trap moisture as they age.
Renew cavity wax every five to 10 years and underbody wax every two to five years depending on use. Touch in upper-body stonechips promptly using an artist’s brush, a primer and a top coat. Spray aerosols into their lids and allow to thicken before brushing on.
Treat rusty spots by scraping, applying rust remover and then painting. Polish keeps water out of the paint’s pores. Periodically probe drain holes in the bottoms of doors and sills. Beware signs of trouble in areas that have been subject to major repair or restoration: the repair work may be hiding a multitude of sins.