Reliability Guide
Common Smart Problems
Select a model below to discover known faults, common MOT failures, estimated repair costs, and buying tips.
Select a Smart Model
Smart Forfour (453)
2015 – 2021
3 documented issues
Smart Fortwo (453)
2014 – 2024
4 documented issues
Smart Fortwo (451)
2007 – 2014
3 documented issues 2 severe
Smart Forfour (454)
2004 – 2006
3 documented issues 1 severe
Smart Roadster (452)
2003 – 2005
3 documented issues 2 severe
Smart Fortwo (450)
1998 – 2007
4 documented issues 3 severe
Brand-wide Smart Problem Patterns
SAM Unit Water Damage: Water ingress into the Signal Acquisition and Management (SAM) unit causes catastrophic electrical failures.
Engine Longevity (600/700cc): These tiny engines often require a top-end rebuild between 60,000 and 80,000 miles due to piston ring wear.
Three Bars of Death: A common gearbox fault display indicating a failure in the gear selection or clutch actuation system.
MHD Belt Failure (451): On Mild Hybrid Drive models, the drive belt can snap, leading to instant overheating and engine damage.
Water Ingress (Roadster): Almost all Roadsters leak to some degree, which can destroy the dash-mounted electronics and SAM.
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