Smart Crossblade

Porous or cracked charge-air hoses prevent correct wastegate control. The engine goes into limp mode and the turbo is often unnecessarily replaced. This is the most common cause of power loss on the 450.

Symptoms: Sudden power loss, Smart won't get above 100 km/h, feels throttled, engine warning light illuminated

The exhaust manifold on the 450 has internal dividing walls that can crack and damage the turbocharger. Small cracks in the manifold cause boost pressure loss at full throttle.

Symptoms: Power loss under full throttle, metallic noises from the engine bay, irregular boost pressure

The piston ring grooves in the M160 wear out, allowing oil into the combustion chambers. Burning oil creates carbon deposits on the exhaust valves, which can then burn out.

Symptoms: Increased oil consumption, blue smoke from exhaust, power loss, carbonised exhaust valves

The Smart 450 has one front and two rear engine mounts, which are heavily loaded by the compact layout and three-cylinder vibrations. Failure announces itself with rattling.

Symptoms: Rattling noises at low speeds and over light bumps, increased vibrations at idle

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.