2004 BMW Z4 3.0L Petrol · RA04 UFS

The 2004 BMW Z4 presents a worsening mechanical trend despite passing its most recent MOT on 23 March 2026 at 111,522 miles. While the vehicle remains roadworthy, the progression of corrosion advisories indicates deteriorating underbody and structural integrity. The tester flagged a corroded nearside rear coil spring in the latest test, a notable escalation from previous years. Recurring warnings regarding the rear sub-frame, suspension arms, and sills point to persistent, unaddressed rust rather than isolated incidents. This pattern suggests the underbody is degrading faster than the mechanical components are wearing out. Averaging roughly 5,069 miles per year, this Z4 has seen exceptionally light use over its twenty-two-year lifespan. The MOT records reveal a distinct drop-off in recent activity; the vehicle covered only 668 miles between the August 2024 test and the March 2026 test. Such prolonged stationary periods likely exacerbated the corrosion issues, as moisture accumulates without the protective heat and movement of regular driving. Low mileage typically preserves consumables, but here it has allowed dormant moisture to attack the steel brake lines and suspension mounts. A prospective buyer must thoroughly inspect the underside for structural corrosion. The repeated advisories regarding corroded brake pipes covered in grease indicate a cost-cutting approach to maintenance, applying temporary sealant rather than replacing the compromised lines. The tester also noted corrosion on the rear sub-frame, suspension arms, and sills, requiring close examination to ensure the structural integrity has not progressed beyond the condition noted in 2024. Suspension components demand particular attention. The 2023 failure for seriously weakened front Macpherson strut mountings was apparently rectified, but the 2026 advisory for a corroded nearside rear coil spring suggests the suspension is now suffering from surface degradation. Check the shock absorber casings for damage and assess the condition of all brake hardware before committing to a purchase.