1986 Porsche 911 3.3L Petrol · C836 NGJ

The most recent MOT recorded on 2 September 2023 resulted in a failure for excess carbon‑monoxide in the exhaust emissions test (regulation 8.2.1.2 (b)). All preceding examinations from 2016 to 2022 were passes, the only noted advisory being a severely deteriorated constant‑velocity boot on the off‑side rear driveshaft in July 2022. The pattern suggests a generally stable maintenance record until the latest emissions failure, which may indicate emerging engine wear, a leaking exhaust manifold, or a failing catalytic converter rather than a sudden decline in overall upkeep. At 156 568 miles the car averages just under 4 000 miles per annum over its forty‑year life, a figure well below the typical usage for a 911 of this vintage. The low annual mileage points to periods of limited running or prolonged storage, which can be favourable for wear‑related components but also raises the possibility of age‑related degradation such as rubber cracking, corrosion in hidden areas, and fluid breakdown. No large mileage spikes are evident, so the wear on consumables such as brake pads, clutch discs and suspension bushings is likely to be modest, though the long idle periods can allow moisture to settle in bearings and joints. Given the emissions failure, a prospective buyer should have the exhaust system inspected for cracked manifolds, loose clamps, or a perforated catalytic converter, and verify the condition of the oxygen sensor and any aftermarket modifications that could affect the air‑fuel mixture. The deteriorated CV boot noted in 2022 should be replaced promptly, as a leaking boot can allow grease loss and eventual joint failure, which would manifest as clunking or vibration from the rear axle under acceleration or cornering. A compression test would be prudent to confirm the health of the engine’s cylinders, especially if the carbon‑monoxide level is high due to worn piston rings or valve sealing. Beyond the specific MOT items, the car’s age warrants a thorough visual and tactile survey of the tyre sidewalls for cracking or dry‑rot, as rubber can perish even on low‑mileage tyres. The 12‑volt battery should be load‑tested, and the charging system checked for voltage stability, since long periods of storage can weaken battery plates. Inspect the brake discs for surface corrosion, uneven wear or glazing, and ensure the calipers move freely without binding, as rust can develop on the pistons when the vehicle sits. Finally, confirm that all fluid reservoirs—engine oil, coolant, brake fluid and differential oil—have been changed at calendar intervals, and look for any signs of leaks or sediment that would indicate the need for a complete fluid refresh before committing to the purchase.