Hidden sill, arch and boot-floor corrosion
SeriousBodywork & RustVolvo Owners' Club threads on the 850 repeatedly warn that the sills rot beneath the plastic covers, the rear arches bubble around the wheel-arch seams, and the boot floor pockets either side of the estate loadbay rust through to the outside. Because the rust hides behind trim and under sealant, cars that look tidy can fail the MOT for structural corrosion around sills and rear axle mounting areas. Panel repair is weld-intensive - the honest cost of ownership on any 850 today.
Bubbling paint along the sill edge or behind arch liners, Fresh underseal or filler patches hiding repairs, Rotting boot-floor pockets visible once the carpet is lifted
- Pry back the sill covers and tap-test the metal with a screwdriver handle
- Inspect the rear arch seams and the box-section corners under the battery tray
- Check how many years of MOT remain and whether corrosion has already produced advisories