Smart ForTwo

The ball joint between the actuator and wastegate flap seizes with rust. The flap can no longer open, boost pressure goes unregulated. Engine enters limp mode.

Symptoms: Engine enters limp mode, no power above 3,500 rpm, engine warning light, feels throttled

The oil feed and return lines to the turbocharger become blocked by carbon sludge. The turbo runs dry and is replaced repeatedly, even though the root cause lies in the oil lines.

Symptoms: Whistling noises from the turbocharger, power loss, increased oil consumption, turbo failure

The M160E7 tends to lose oil from various seals. Regularly flagged at the MOT. Short-trip use makes the problem worse through oil dilution.

Symptoms: Oil patches under the vehicle, oil smell from engine bay, dropping oil level, MOT advisories for oil leaks

The automated 6-speed gearbox of the 450 shifts harshly and with a jerk. The clutch actuator wears out, especially when exposed to moisture and contamination.

Symptoms: Juddering on gear changes, delayed gear selection, gearbox refuses to shift to the next gear

The electric clutch actuator gets dirty or fails mechanically. Typical pattern: violent jerk on pull-away, gear cannot be selected, display shows 'N'. Problem often from 80,000 km, sometimes temporarily clears after a short stop.

The SAM unit (fuse and actuator module) sits in the footwell and is at risk from leaking tray seals or blocked drain channels. Water ingress destroys capacitors and circuit tracks, causing electrical failures throughout the vehicle.

Front and rear spring breakages are known on the 450, especially on early production years before 2001. Springs can break suddenly and significantly compromise driving safety. The rear axle is less frequently affected.

On older 450s, the steel brake lines corrode, particularly at mounting clamps and bends. A safety risk in wet regions and on vehicles without regular underbody inspections. Often only discovered at the MOT.

The semi-automatic Softtouch gearbox shifts with noticeable jerks, especially on pull-away and when changing from 3rd to 4th gear. A long shift pause is normal, but excessive jerking indicates a worn clutch or faulty adaptation.

Seals on the windscreen, rear window and door frames harden over the years and allow water into the interior. Very common on vehicles over 10 years old; footwells and boot are affected.

Older 450s with heavy city use show corrosion on the sills and underbody. Although the bodywork uses plastic outer panels, the steel frame (Tridion cell) and weld seams can rust if not properly maintained.

The front axle control arm bushings wear out and become sloppy. Particularly susceptible to early wear with frequent city use involving kerb contacts. Results in poor straight-line tracking and knocking noises over uneven surfaces.

The steering rack develops play with age and can develop leaks. Hydraulic fluid escapes and steering becomes increasingly imprecise. Repair kits are available; a full replacement costs considerably more.

The ABS tone rings at the wheel hubs corrode and lose electrical contact. The ABS system then fails sporadically or permanently, with the warning light illuminating. Regular checks are advised on older vehicles that have seen many winters.

The indicator stalk develops increased contact resistance over time, which can cause the switch lever to overheat. In the worst case, contacts melt. A known and documented problem on the 450.

The 450 cabriolet hood is operated by two independent electric motors. Over time these lose synchronisation — one side runs ahead, the hood jams or can no longer be opened.