Common Problems with the
2006 Caterham Seven (Sigma, Duratec & Suzuki)

The De Dion tube can develop hairline cracks near the welds on cars used heavily on track or with stiff suspension.

The vibrations from the Duratec engine, especially in higher states of tune, can crack the engine mounting brackets.

The Seven's mild-steel spaceframe chassis is protected by powder coating, but the coating chips easily from stone strikes and, once breached, the steel can rust from the inside out. Corrosion typically starts at welds, joints and suspension mounting points where salt and moisture become trapped, and untreated chips can perforate the chassis tubes - an MOT structural issue and an expensive repair. Caterham advises that any repaired chassis section must be re-rust-proofed, because the repair breaks the original powder-coat protection.

On Ford-era Sevens the rear lights can stop working without warning. Common causes are chafed or corroded wiring in the loom, a failed brake-light switch, and mud or moisture gathering on the rear lamp connectors; cars with the later integrated LED rear lamp units have also suffered poor earth connections that cut the lamps intermittently. The Seven has no electronic warning lamps for its lighting circuits, so a failed rear light can go unnoticed until another road user - or the MOT tester - spots it. DVSA MOT data shows lamps, reflectors and electrical equipment are the largest single failure category on the Caterham Seven, present in 62.2% of failed tests.