Smart Forfour 0.9 TCe problems
The Smart Forfour used the 0.9 TCe from 2014 to 2019. 5 documented faults affect it; the most important is “coolant leak at the thermostat housing” (high severity, common). Our verdict: “With caution”. Among the documented engines of the Smart Forfour, the safest option is the 1.0 SCe (B4D).
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Engine score on this car
5.1 out of 10Acceptable reliability
Only counting the faults that affect the versions and years of the Forfour. How we calculate it
Overall score for the Smart Forfour
6.1 out of 10Acceptable reliability
Engines, gearbox, suspension, brakes, electronics and the rest of the car. See breakdown
Renault-Nissan-Daimler 0.9 TCe (H4Bt / M281 / Nissan HR09DET) · Petrol
- Faults that affect it
- 5 · 3 of high or critical severity
Verdict for the version it uses
0.9 TCe 90 (H4Bt, 2012-2024)2012–2024 · 90 hp · H4Bt-400, H4Bt-408, H4Bt-410
With cautionThe reliability record is positive and better than that of its sibling the 1.2 TCe, without the oil consumption or rate of chain problems so well documented for that engine. Check the coolant history (leak at the thermostat housing) and, to a lesser extent, any history of noise or work on the timing chain before buying.[3][4]
Faults that affect the Forfour
- High severityFrequency: CommonCoolingCoolant leak at the thermostat housingThe 0.9 TCe can lose coolant through the thermostat housing (calorstat) gasket. It is the most-cited fault of this engine: if not detected in time, the low level can end up damaging the head gasket.
- Critical severityFrequency: OccasionalTimingTiming chain or tensioner failureThe 0.9 TCe's timing chain tensioner can lose effectiveness over time. It is a minority of cases, but when the chain jumps the damage is serious: there is a documented case with a complete engine replacement at 80,000 km.
- High severityFrequency: RareTurboTurbocharger wear or failureThe 0.9 TCe's turbo can lose performance or fail, although the available statistics put it as an infrequent fault on this specific engine.
- Low severityFrequency: RareInjectionJerking due to an injection calibration that needs reprogrammingSome 0.9 TCe engines show slight jerking when accelerating because of an injection calibration that is corrected by reprogramming the ECU, without it being mechanical damage.
- Low severityFrequency: RareLubricationOil consumption (uncommon on this engine)Unlike other engines in the same family, the 0.9 TCe does not show a widespread pattern of excessive oil consumption: the sources document only a minority of cases.
What to check before buying a used Smart Forfour 0.9 TCe
Each point comes from a documented fault that affects this car. You can tick them off as you inspect it.
If it has the 0.9 TCe (2014–2019)
Coolant leak at the thermostat housing
High severityTiming chain or tensioner failure
Critical severityTurbocharger wear or failure
High severityOil consumption (uncommon on this engine)
Low severityOther engines and gearboxes of the Smart Forfour
Score for each one with the faults that affect this car, from best to worst.
Faults of the Smart Forfour outside the engine
Suspension, brakes, electronics and the rest of the car: they occur with any engine.
- Critical severityFrequency: OccasionalSuspensionFront left hub carrier with insufficient strength (2017 campaign)A Safety Gate alert (41/2017) and the DVSA cover Forfours and Fortwos built between March and June 2017 whose front left hub carrier may lack the necessary strength and break, with loss of control. It is checked and replaced if necessary at an official dealer.
- High severityFrequency: OccasionalBrakesHandbrake: the lever gains travel because of the cable adjustment and may not hold the carYes: a Safety Gate alert (39/2017) covers type 453 Forfours built between November 2014 and October 2015 because the cable adjustment part of the parking brake weakens and the lever gains travel, so the brake may not apply the necessary force. It is checked at an official dealer.
- High severityFrequency: OccasionalAirbags and safetyRear seat backrest anchorage with insufficient strength in a frontal crashIn 2016 Safety Gate published an alert (A12/0766/16) because the rear seat backrest anchorage of the Forfour, built from September 2014 to December 2015, may not withstand a frontal crash with a heavy load behind it. The backrest could come loose and fold forwards.
- High severityFrequency: OccasionalGearbox and clutchGear selector bowden cable that can come loose and stop P engaging or disengagingThe DVSA lists a recall (R/2016/198) over the gear selector bowden cable, which can come loose and stop the P position engaging or disengaging, with a risk of the car rolling. It affects Forfours and Fortwos from April 2016, 49 vehicles in the UK.
- Medium severityFrequency: OccasionalElectrical system12 V battery: a common reason for roadside assistance on 2015 to 2017 ForfoursThe German ADAC's breakdown statistics, reproduced by car-recalls.eu, point to the battery as a typical weak point of 2015 to 2017 Forfours, the first years of the W453 generation. The source gives neither the cause nor the cost.
Buying a Smart Forfour 0.9 TCe?
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The Smart Forfour has 6 documented recalls and campaigns. See which ones and how to find out if they affect you
Frequently asked questions
Is the Smart Forfour 0.9 TCe reliable?
The Smart Forfour used the 0.9 TCe from 2014 to 2019. 5 documented faults affect it; the most important is “coolant leak at the thermostat housing” (high severity, common). Our verdict: “With caution”. Among the documented engines of the Smart Forfour, the safest option is the 1.0 SCe (B4D).
What faults does the Smart Forfour 0.9 TCe have?
The documented ones that affect this car are: coolant leak at the thermostat housing (high severity), timing chain or tensioner failure (critical severity), turbocharger wear or failure (high severity), jerking due to an injection calibration that needs reprogramming (low severity) and oil consumption (uncommon on this engine) (low severity).
Which engine should you choose for the Smart Forfour?
None has a «Buy» verdict; the safest option is the 1.0 SCe (B4D), with a «With caution» verdict.
Own a Smart Forfour 0.9 TCe? Tell us what faults you have had and at how many kilometres. Report your fault.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- Mercedes-Benz M281 engineWikipedia (inglés) · Other source · consulted 27 September 2026
- Smart ForfourWikipedia (inglés) · Other source · consulted 27 September 2026
- Moteur H Renault-NissanWikipedia (francés) · Other source · consulted 27 September 2026 · in French
- Fiabilité des 0.9 TCeFiches-auto.fr · Motoring press · consulted 27 September 2026 · in French