Common Smart Problems
Smart (Swatch Mercedes ART) revolutionized urban mobility with the original Fortwo. While owned by Mercedes-Benz, these cars have their own unique set of mechanical challenges, primarily centered around their specialized automated manual transmissions and compact engine packaging. In the UK, they are tax-efficient and easy to park, but maintenance can be surprisingly expensive due to the tight engine access and sensitivity to water ingress.
Common Smart trouble spots
- •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.
What to check on used Smarts
- ✓On 450, 451, and Roadster models, the "automated manual" gearbox is the most critical component. Test for smooth engagement and no "three bars of death" on the dash.
- ✓Check the carpets and footwells for dampness. Water ingress is the number one killer of Smart electronics (SAM units).
- ✓Verify engine health on older 600cc and 700cc units; high oil consumption often signals an impending need for a rebuild.
- ✓The 450 and 451 engines have six spark plugs (two per cylinder). The bottom three are hard to reach and often neglected in DIY or cheap servicing.
- ✓Inspect the rear coil springs; they are a very frequent MOT failure point on UK roads.
Select a Smart Model
Smart Forfour (453)
The four-door version of the 453. Like the Fortwo, it is rear-engined and shares parts with the Renault Twingo. It has an incredibly small turning circle for its size.
Smart Fortwo (453)
Shared platform with the Renault Twingo. This model offers a much better ride and the option of a proper manual gearbox or a dual-clutch (Twinamic) transmission.
Smart Fortwo (451)
The 451 generation moved to a 1.0L Mitsubishi-sourced engine (naturally aspirated or turbo). It is significantly more robust than the 450 but introduced its own unique issues, particularly with the MHD system.
Smart Forfour (454)
A front-engined, front-wheel-drive Smart based on the Mitsubishi Colt. Much more conventional than other Smarts, but the automated manual version still has actuator issues.
Smart Roadster (452)
A lightweight, fun sports car that shares many components with the 450 Fortwo. It is famous for its handling and infamous for its leaks.
Smart Fortwo (450)
The original Fortwo is tiny and clever, but it is also the most fragile. It uses a 600cc or 700cc turbocharged 3-cylinder engine. In the UK, many have succumbed to engine wear or electrical "death by water," making a well-maintained example a rare find.
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