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Smart (mcc) Fortwo Problems & Known Issues

The most common Smart (mcc) Fortwo problems ranked by severity — what to watch for, what it costs to fix, and what happens if you ignore it.

Generations

450 — First Generation
1998–2007
0.6L Petrol, 0.8L CDI
451 — Second Generation
2007–2014
0.8L CDI, 1.0L Petrol
453 — Third Generation
2014–2020
0.9L Turbo, 1.0L Petrol

Top issues to watch for

The most serious Smart (mcc) Fortwo problems ranked by severity. We track 5 known issues — here are the ones you need to know about first.

Major
Engine mount failure (451/453)
451, 4532007–202020k–80k miles
The engine mounting brackets on 1.0L petrol engines deteriorate and crack, causing excessive engine movement. MOT data shows this model fails at 16.4x the national average for engine mount defects between 20,000-80,000 miles. The rear mount is particularly prone to failure due to vibration from the three-cylinder engine layout. Failed mounts cause harsh vibration through the cabin, poor gear selection, and can damage surrounding components.
What happens if ignoredFailed engine mounts cause increasing vibration, make gear selection difficult, and can lead to damage of exhaust components, electrical connections, and cooling hoses if the engine moves excessively. Replacement involves engine-out work at a specialist. Driving is possible but uncomfortable and risks secondary damage.
Independent garage
£300–£500
Specialist
£400–£600
Main dealer
£600–£900
Parts only
£80–£150
Major
Emissions system failure - lambda sensor (451/453)
451, 4532007–20200k–100k miles
Lambda sensor failures cause emissions to exceed manufacturer limits and trigger management light illumination. MOT data shows this model fails emissions tests at 8.6x the national average, with particular issues on 0.9L turbo engines from 20,000 miles. The three-cylinder engine layout creates uneven exhaust pulses that stress the lambda sensors, causing premature failure. Failed sensors result in poor fuel economy, rough running, and MOT failure.
What happens if ignoredFailed lambda sensors cause MOT failure, poor fuel economy, catalyst damage if left untreated, and potential engine damage from incorrect fuelling. The car remains driveable but will fail MOT and may trigger limp-home mode. Replacement is straightforward but catalyst replacement can be expensive if damage has occurred.
Independent garage
£150–£250
Specialist
£200–£300
Main dealer
£300–£450
Parts only
£80–£150
Major
Fluid leaks affecting safety (451/453)
451, 4532007–202020k–80k miles
Smart Fortwo models from the 451 and 453 generations (2007-2020) can develop significant oil leaks from various engine seals and gaskets, particularly affecting the oil pan, valve cover, and transmission areas where the compact engine bay concentrates heat and accelerates seal deterioration. These leaks typically emerge between 20,000-80,000 miles and may progress from minor seepage to substantial fluid loss that can create hazardous road conditions or lead to catastrophic engine damage if oil levels drop critically low. Oil leaks can result in MOT failure under dangerous defects if they pose a risk to other road users or significantly affect braking components. Professional inspection should assess leak severity and source, as some repairs may require engine removal due to the Fortwo's unique rear-mounted engine configuration.
What happens if ignoredSignificant fluid leaks cause MOT failure when they pose safety or environmental risks. Oil leaks can lead to engine seizure on small-capacity engines if levels drop critically. Coolant leaks cause overheating and potential head gasket damage. Most leaks are repairable but require immediate attention on these small-capacity engines.
Independent garage
£150–£400
Specialist
£200–£500
Main dealer
£350–£750
Parts only
£25–£100
Minor
Suspension component wear (451/453)
451, 4532007–202040k–100k miles
Suspension bushes and joints wear at 3.8x the national average, typically affecting front suspension components from 40,000 miles. The short wheelbase and firm suspension setup on Smart cars places higher loads on bushes and ball joints. Front anti-roll bar bushes and track rod ends are most commonly affected. Worn components cause poor handling, tyre wear, and MOT failure.
What happens if ignoredWorn suspension components cause poor handling, rapid tyre wear, and MOT failure. The car remains safe to drive but handling becomes progressively worse. Individual components are relatively inexpensive but labour costs add up if multiple items need replacement simultaneously.
Independent garage
£200–£400
Specialist
£250–£450
Main dealer
£400–£650
Parts only
£50–£120

1 more known issues tracked

Including wear items, electrical niggles, and generation-specific problems. Check a specific car to see which issues apply to its age and mileage.

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MOT failure hotspots

Based on DVSA MOT test data. These are the items where the Smart (mcc) Fortwo fails at a significantly higher rate than the average car.

Engine mounting/bracket severely damaged or det...
Bodywork · 100-120k miles
MOT failure rate: 38x the fleet average
Sample: 249 tests
Emissions failure
Exhaust & Emissions · 20-40k miles
MOT failure rate: 18x the fleet average
Sample: 8,723 tests
Window tint too dark
Wipers & Windscreen · 40-60k miles
MOT failure rate: 13x the fleet average
Sample: 10,699 tests
Any part of the noise suppression system insecure
Exhaust & Emissions · 60-80k miles
MOT failure rate: 12x the fleet average
Sample: 3,974 tests
Headlight fault
Lights & Electrics · 20-40k miles
MOT failure rate: 11x the fleet average
Sample: 273 tests
Tyres on the same axle or on twin wheels are di...
Tyres · 20-40k miles
MOT failure rate: 9.1x the fleet average
Sample: 5,727 tests

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Related

Smart (mcc) Fortwo reliability FAQs

What are the most common problems with the Smart (mcc) Fortwo?

The Smart (mcc) Fortwo has 5 known issues across 2 severity levels. The most common problems relate to Engine mount failure (451/453) and Emissions system failure - lambda sensor (451/453).

Is the Smart (mcc) Fortwo reliable?

The Smart (mcc) Fortwo has 0 dangerous and 3 major known issues. No dangerous issues are tracked, which is a positive sign.

How much does it cost to fix Smart (mcc) Fortwo problems?

Repair costs range widely. The most significant issue (Engine mount failure (451/453)) costs £300–£500 at an independent garage. Minor issues can be under £200. Always get a full inspection before buying.

Which Smart (mcc) Fortwo generation is most reliable?

The 450 (1998–2007) has the fewest dangerous issues (0). However, condition and service history matter more than generation — a well-maintained earlier car can be more reliable than a neglected newer one.