Smart ForTwo
The smallest production diesel of its time. Fundamentally unsuited to city driving and short trips — precisely the use case of most Smart owners. DPF problems, turbo wear and high repair costs relative to vehicle value make the CDI an engine to avoid. The petrol engines are the far better choice.
Diesel cabrio without a punchline
41 hp CDI in the cabrio — even the open roof can't rescue the clattering diesel with softtouch. Pure economy car for high-mileage drivers.
Engine Weaknesses 4
On Euro 5 models (54 hp) a sensor was incorrectly positioned. In winter, ice can form in the intake tract and damage the turbocharger. Limp mode activates.
Symptoms: Engine limp mode in winter, power loss, whistling noises from the turbocharger, engine warning light
The injectors of the OM660 coke up through frequent short-trip use. At 150,000 km and beyond, cold-start problems and rough running appear.
Symptoms: Poor cold start, rough running, power loss, increased consumption, heavy smoke
The DPF on the Smart CDI clogs frequently because the vehicle is typically used for short trips. Regeneration requires 20–30 minutes of sustained driving at around 120 km/h.
Symptoms: Power loss, DPF warning light, increased consumption, engine enters limp mode, regeneration does not complete
The EGR cooler on the OM660 develops leaks and loses coolant. The coolant enters the intake tract and can damage the engine.
Symptoms: Dropping coolant level, white smoke from exhaust, coolant smell, possible engine overheating
Vehicle Weaknesses 14
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.
The tailgate hinges wear out, causing the hatch to no longer latch properly or to hang crooked. The plastic trim in the rear area then cannot be closed flush.
The bonded PVC rear window in the soft-top material becomes porous from turbulence at the rear of the vehicle and UV exposure. It can crack or detach from the fabric.