Rust is the most expensive item
Mechanicals can be overhauled. Structural sheet metal in the sills, floor and mounts costs several times the purchase price once it has to be welded, straightened and painted. That is why every viewing starts at the metal, with a torch, a magnet and, if possible, a paint-thickness gauge.
The places that belong to one model are in the buying advice. Here it is what applies to almost every classic.
Surface against structure
Surface rust on an unprotected underbody or on an exhaust clamp is work, often not a drama. Structural rust in a sill, chassis rail, spring mount, strut tower or floor pan is a project. The MFK draws the same line: structural parts rusted through fail.
Useful ways to tell them apart:
- The knock: dull and soft instead of tinny
- The magnet: holds poorly where there is filler or a thick PVC layer
- The thickness: factory paint usually sits in a narrow band; wild jumps and values beyond 400 micrometres on smooth panels point to a respray and filler
- A look from below at the inside of the sills and into the jacking points
The zones that almost always count
- Wheel arches and rear wing edges
- Sills and their inner rails
- Jacking points
- Floor pans under the carpets, especially at the front
- Scuttle, sunroof cassettes, rear window frames
- Spare-wheel well and tank well
- Spring mounts and strut towers
Lift the carpets. A smell of mould when you open the door points to wet in the floor, not to "the smell of a car that has been standing".
Fresh underseal
Fresh, thick, black, still soft: that can be care, or a cover. The two look the same. At the edges, and in places the seller does not expect (inner sill, behind the trim), the truth shows. A car that has "just had the underside protected" and otherwise has no history, you treat as unprotected, plus a layer you cannot see.
After the diagnosis
Small, dry spots on non-structural parts: a deduction on the price, and a plan. Structural metal rusted through: either a deliberate project with a budget, or you walk away. The checklist has the points; an appraisal on a lift, on an expensive car, costs less than a chassis-rail hole you missed.
If you have welding done: only in a workshop that is competent with sheet metal, with photographs and, where the structure is affected, with an eye on the next MFK and on veteran status.