452 2003–2006 Roadster (mid-engine sportscar)

2003–2006 Smart Roadster (452)

Gas (M160 0.7L turbo 3-cyl), 80–82 hp standard or 101 hp Brabus, RWD, mid-engine, 6-speed Getrag single-clutch automated manual with paddle shifters

Is this you? If your Smart is low and wide, has the engine between the seats and the rear axle, and probably leaks somewhere, you're in the right place.

Jump to manuals & downloads ↓ First 30 days checklist

About this generation

The 452 Roadster is the cult car in Smart's history. Built only from 2003 to 2006, it was Mercedes' attempt to put the Fortwo platform under a low, wide, mid-engine sportscar body. It worked beautifully and didn't sell well enough — production ended after roughly 43,000 cars. Today it's the Smart that gets restored, modified, and shown at concours rather than scrapped. If you bought one, you bought into a small global community that treats this car as a piece of Mercedes' weird-and-wonderful era, not a disposable city car.

Mechanically the 452 takes the M160 0.7L turbo three from the 450 and mounts it differently. The 450's engine sits behind the rear axle. The 452's engine sits between the seats and the rear axle — proper mid-engine, like an old Lotus. The two cars share many parts but they handle nothing alike. The 452 turns in eagerly, has more steering feel than any Fortwo, and rewards smooth inputs the way a Lotus Elise does. It's slow on paper (80 hp standard, 101 hp Brabus) and quick in the way that matters on a winding road.

And we have to talk about the water. The 452 is famous for water leaks. Not occasional, not intermittent — chronic. Mercedes literally published a 48-page 'Water Penetration Remedial Measures Guide' for the chassis: the same document is in the Resources section below. The roof seals, the trunk drain channels, the rear quarter panels, and the windscreen surround all leak in some combination on most cars. Water finds its way to the SAM module under the passenger floor and kills it. Buying a 452 means accepting you'll be sealing things until the day you sell it. If you can't accept that, buy a 451 instead.

The transmission is the same Getrag single-clutch family that's in the 450 and 451 — single clutch, a robot, a pause at every upshift. The 452 ships with paddle shifters as standard, which lets you drive in manual mode permanently. Most enthusiast owners do exactly that and use the auto mode only in stop-and-go. Driven in manual with paddles, the gearbox actually suits the car — you choose the shift point and the box snaps it in. It's not a modern dual-clutch but it's far more enjoyable in the 452 than in the 451 because you have direct control.

The 452 was never officially sold in North America. It went to UK, EU, Japan, and a small AU import market. Grey-market 25-year-rule imports to the US start in 2028 — a steady trickle of enthusiast cars will follow. If you're reading this in the UK, EU, or AU, you're the volume audience for this page.

Quick specs

Engine options
  • 0.7L M160 3-cylinder turbo (80 hp / 81 lb-ft) — Roadster standard 2003–2006
  • 0.7L M160 3-cylinder turbo (82 hp tune) — Roadster Coupe standard
  • 0.7L M160 3-cylinder turbo Brabus (101 hp) — Brabus Roadster and Brabus Roadster Coupe
  • Brabus V6 BiTurbo 3.8L (~170 hp) — prototype only, never production. Approximately 10 cars built. Richard Hammond drove one on Top Gear.
Gearbox
6-speed Getrag single-clutch automated manual with paddle shifters as standard. Same family as the 450/451 — one clutch, a robot, a pause between shifts. Paddle shifters and standard manual mode make it far more livable than in the Fortwo chassis.
MPG / Range
44–48 MPG (UK gallons) standard, low 40s on Brabus — cruisey but not particularly economical for the engine size
Length
11 ft 0 in (3,360 mm) — significantly longer than any Fortwo
Weight
1,830–1,940 lb (830–880 kg) depending on Roadster vs Coupe and trim
Fuel
Premium unleaded (95 RON / 91 octane) — Mercedes-spec, not optional
Built in
Hambach, France
Seats
2
Cargo
5.9 ft³ in the front trunk, ~3 ft³ in the rear. Two trunks because the engine is in the middle.
Safety
Tridion safety cell, dual front airbags, ABS standard, ESP standard. No side airbags. Roof structure on Roadster is the cloth top with a small steel hoop; Coupe variant has a glass targa roof and a fixed rear pillar.

Downloads & resources

The manuals, diagrams, and quick references that ship with this chassis. PDFs open in a new tab; on-site pages are owner-to-owner walkthroughs.

Manuals Workshop Service Manual (450/451/452/454) · PDF · 4,602 pp
Diagrams SAM Wiring Schematic (452, RHD) · PDF · 1 pp SAM Electrical Schematic (452, DE) · PDF · 14 pp
Reference Fluids & Capacities reference Maintenance Schedule Pre-Purchase Inspection Checklist
Bulletins Water Leak Remedial Measures Guide (452) · PDF · 48 pp

Missing a manual you'd expect to see? Email us — if it exists, we'll add it.

Trims & variants — what each one meant

Smart's trim names look interchangeable across generations, but they mean slightly different things on each chassis. Here's what the labels actually got you on the Roadster (452).

  • Roadster (cloth roof)

    The base 452 body. Power-folding cloth top with two removable rails on either side of the cabin. Looks like a small open-top sportscar with the roof down. The most common 452 in the UK and EU.

  • Roadster Coupe (glass targa)

    Same chassis with a fixed rear pillar and a glass targa roof — more weather-tight and a different silhouette. Slightly heavier than the Roadster. Sometimes called the 452 Coupe in shorthand.

  • Brabus Roadster / Brabus Roadster Coupe

    Factory hot-rod variants. 101 hp tune (vs 80–82 hp standard), uprated suspension, larger Brabus wheels, body kit, and Brabus interior trim. The Brabus Coupe is the most desirable production 452 in the UK enthusiast market.

  • Bluestar (special edition)

    A 2005 limited-edition Roadster Coupe in metallic blue with body-color interior trim accents. Small production run, popular with collectors today.

  • Finale Edition (special edition)

    The 2006 farewell edition marking the end of 452 production. Special paint, badging, and trim. The most collectible regular-production 452 made.

  • Brabus V6 BiTurbo (prototype)

    Approximately 10 prototype cars built with a Mercedes 3.8L V6 BiTurbo from the SLK/CLK platform shoehorned into the 452's mid-engine bay. Made roughly 170 hp and turned the 452 into a serious sportscar. Never sold to the public. Richard Hammond drove one on Top Gear and owners of the survivors are well-known in the global Smart community.

The first 30 days

If you just bought a Roadster (452), this is the order to do things in. Stay ahead of these and you'll save yourself a lot of money.

  1. Read the Water Leak Guide cover-to-cover

    Mercedes published a 48-page document specifically because every 452 leaks water somewhere. The guide is in Resources above. Read it. It walks through the trunk drain channels, the roof seals, the windscreen surround, the rear quarter panel seams — every known ingress point on the chassis with photos. Knowing where to look saves hundreds of hours of guessing.

  2. Inspect the SAM module under the passenger footwell

    The SAM (signal acquisition module) lives under the passenger floor. Water that gets into the cabin or the trunk drains often finds its way there. Pull the passenger carpet, look for water marks, corrosion on the connector pins, or any moisture. A wet SAM is the most expensive failure on the chassis — the module is hard to source and matched to the car. Catching dampness before it kills the SAM is the single highest-value first-week task.

  3. Drive in manual mode and use the paddles

    The 452's gearbox is a single-clutch automated manual — same family as the 450/451 trans. Auto mode pauses at every upshift. Manual mode, with the paddles, gives you direct control. Most enthusiast owners drive in manual permanently. Try it for a week and see if you prefer it. The 452 is far more enjoyable in manual than the Fortwo because you actually have a sportscar chassis to apply the paddles to.

  4. Check the turbo health

    The M160 turbo runs hot and failures cluster around 70–90k mi. Symptoms: oil consumption, blue smoke under boost, low boost pressure, whining noise. Pull the inlet hose and look at the compressor wheel — chips, shaft play (vertical or radial movement when you wiggle it), or excessive oil residue are warnings. A turbo that's about to fail can take the engine with it; a turbo that's been replaced recently is a strong selling point.

  5. Confirm fluid levels and quality

    Engine oil (Mercedes 229.3/229.5 spec, 5W-40 or 5W-30 typical for the M160 turbo), coolant (Mercedes spec, ~5L total), brake fluid (DOT 4), and the Getrag transmission fluid. Don't substitute the trans fluid — the Mercedes spec matters.

  6. Find the service history and confirm the turbo and water pump records

    On UK cars, the DVLA MOT history tool shows mileage progression and advisories. EU cars vary by country. Specifically look for any documented turbo replacement, water pump replacement, or major water leak repair. Cars with documented water-leak remediation work are worth more than 'it doesn't leak now' verbal claims.

  7. Find an indie before you need one

    The 452 community is small but tight. Use the [Mechanic Directory](/mechanic-directory/), the smart-club.co.uk Roadster section, and the dedicated 452 Facebook groups to find shops that have actually worked on the chassis. Generic 'we'll work on anything' shops will not save you money on this car.

  8. Take a baseline scan

    An iCarsoft i980 (UK/EU) or Foxwell NT530 reads Smart-specific modules — engine, transmission, ABS, SAM, airbag/SRS. Pull all module faults, save the report, you have a starting point. Pay particular attention to any historic SAM water-related codes.

Join the communities

Smart left North America in 2019. The communities below are how owners keep these cars on the road today — tribal knowledge, shop recommendations, parts swaps. Join two or three and lurk for a week before posting.

Global

  • Evilution.co.uk Forum

    The deepest enthusiast-run Smart resource on the web. The Roadster section is unusually strong — Evilution's owner has been in the chassis since launch and has documented every water leak path, every electrical quirk, and every Brabus-specific job.

  • smartroadster.org / SmartRoadster.net Forum

    Roadster-specific community archive. International owners, regional meets, dedicated water-leak threads.

  • smartcarforums.com Forum

    Long-running multi-region forum. The 452 sub-forum has 20 years of accumulated tribal knowledge — search before you post.

  • @SmartCarVideos (this site) YouTube

    670+ curated videos organized by generation and job type — the playlist library that goes with smartcarmanuals.com.

  • Evilution YouTube YouTube

    Companion channel to the website. Concise, hands-on, no filler. Strong on 452 water-leak diagnosis videos.

North America

  • Smart Car of America Forum

    North-American-skewed forum. Roadster content is mostly speculative — the 25-year rule imports start in 2028 — but the community has thought hard about which Roadsters to import and which to avoid.

  • r/smartcar Reddit

    Mixed-region subreddit. Roadster traffic is mostly UK/EU users; the rare grey-market or future 25-year-rule import owner shows up periodically.

UK & Europe

  • smart-club.co.uk Forum

    UK-focused. The Roadster section is one of the most active sub-forums on the site — dedicated meets, restoration threads, and a steady flow of buying/selling.

  • smartroadsterforum.de Forum

    German-language Roadster forum. Decades of EU-specific knowledge, and the place to ask about parts the UK shops don't stock.

  • Smart Roadster Owners Club (Facebook) Facebook

    Login required, worth it. UK/EU-skewed Roadster-specific group — most direct match for this page.

  • Smart Car Owners UK (Facebook) Facebook

    Login required, worth it. General Smart UK group with a dedicated Roadster sub-thread for sales and tech.

Australia

  • Smart Car Australia (Facebook) Facebook

    Login required, worth it. AU 452s came in as RHD UK imports in small numbers. Regional indie shops and import experience live here.

Watch this stuff before you wrench

A handful of videos that'll save you an afternoon — @SmartCarVideos first, then the deep enthusiast channels.

Browse the full Video Library →

Top maintenance items

The owner-friendly jobs that keep this chassis running. Each card is a deeper guide on this site.

Engine oil & filter change

View guide →

Spark plug replacement

View guide →

Engine air filter

View guide →

Cabin air filter

View guide →

Brake pad replacement

View guide →

Browse all maintenance guides →

Common problems & what to watch

The things that actually fail on this chassis. Cards link to deep guides with cheap-first checks and parts pricing.

Water leaks — the chassis-defining 452 problem (Mercedes published a 48-page guide)

Shop

Diagnose code →

Browse all fault codes →

Recalls

Recall repairs are free at any Smart-authorized Mercedes dealer regardless of how many owners back the campaign was issued. Look up your VIN below.

Outside the US?

The NHTSA database only covers US-market Smarts. For other regions:

Buying one? Look at these first.

Known weak points

  • Water leaks (Mercedes literally published a guide). The 452's defining issue. Trunk drain channels clog, roof seals shrink, the windscreen surround leaks, and the rear quarter-panel seams open up. Water finds its way to the SAM module under the passenger floor and kills it. The 48-page Mercedes Water Penetration Remedial Measures Guide in Resources walks through every known ingress point with photos. Owning a 452 means resealing things on a regular basis. The fix isn't one big repair — it's ongoing vigilance for two decades. See the dedicated [water leak page](/fault-codes/water-leak-451-roadster/).
  • SAM module death by water. When water reaches the SAM under the passenger floor, the module corrodes and various electrical systems die — sometimes the engine won't start, sometimes the lights flicker, sometimes the central locking goes mad. Replacement SAMs are scarce and matched to the car (VIN-coded), so this is one of the most expensive failures on the chassis. Prevention is the strategy: keep the cabin and trunk dry, and pull the passenger carpet at least once to confirm there's no moisture pooling.
  • Turbo failures clustered around 70–90k mi. The M160 turbo on the 452 runs hot in the mid-engine bay and bearings wear out. Symptoms: oil consumption, blue smoke under boost, whining noise, low boost. A failed turbo can grenade the engine if oil is sucked into the intake. If the seller can't show evidence of a turbo replacement on a high-mileage car, factor in £1,200–£2,000 for a rebuild or a remanufactured unit.
  • Water pump failures. The M160 water pump fails at high mileage — coolant leaks at the pump weep hole, eventually the pump bearing seizes and the engine overheats. On a mid-engine 452 this is a more involved repair than on a 450 because access is tighter. Plan for it as a preventive job past 80k mi rather than a wait-for-failure item.
  • Secondary air pump (M160 family weakness). Same SAI weakness shared across the M160/M132/M281 Smart 3-cyl family. The secondary air pump corrodes from condensation and eventually fails, throwing P0410. The car still runs but it won't pass emissions. A replacement pump and (sometimes) check valves are the fix — budget £300–£600 at an indie.
  • Gearbox actuator wear (same family as 450/451 mta). The Getrag mta in the 452 is the same single-clutch family as the 450/451. The clutch actuator wears, fluid leaks, and position sensors drift. Symptoms: harsh shifts that get worse over weeks, three-bar warning, P0805 or P2022 stored. A teach-in procedure can buy time. Eventually the actuator needs replacement — call it £600–£1,200.
  • In-tank fuel pump failures. The fuel pump inside the tank fails on high-mileage 452s — symptoms are fuel pressure drops, hard starting, and stalling under load. Replacement requires dropping the tank, which on a mid-engine 452 is more involved than on a Fortwo. Pelican Parts and the UK Smart specialists stock the pump assembly.
  • Cosmetic plastic and paint fade. After 20 years the 452's body plastics have faded and small trim items (interior buttons, exterior badges, side intake mesh) are getting hard to source. UK breakers and dedicated 452 Facebook parts groups are the realistic supply chain for cosmetic items now.

Pre-purchase test drive checklist

  1. Pull the passenger floor carpet. Look for moisture, water stains, corrosion on the SAM connector. A 452 with a wet SAM is a 452 with a coming bill of £1,000+.
  2. Pull the spare wheel out of the front trunk and check the trunk drain channels. They should be clear; if they're blocked with leaves and grime, water has been pooling there for months.
  3. On a Roadster: cycle the cloth roof up and down twice. Listen for the seal mechanism and the motor. Roof seal replacement is involved.
  4. On a Roadster Coupe: pull the targa panel off and check the seals around the glass. Replace any seal that's compressed flat.
  5. Cold-start the car yourself. Listen for the turbo — any whining noise on idle, any blue smoke when you blip the throttle, is a warning sign.
  6. Drive on boost. The turbo should produce smooth, linear pull from about 2,500 rpm. Hesitation, surging, or low-end flatness can mean a tired turbo or a boost leak.
  7. Pop the engine cover behind the seats. Look for oil seepage at the valve cover, oil residue around the turbo, coolant residue at the water pump weep hole.
  8. Drive in manual mode using the paddles. The shifts should be quick and consistent. Slow shifts, harsh engagement, or random pauses are clutch actuator wear.
  9. Plug in an iCarsoft i980 or Foxwell NT530 and pull all modules. Stored history codes — P0410, P0805, any SAM-water-related codes — tell you what the seller cleared.
  10. Cycle every electrical accessory: windows, mirrors, A/C, all radio functions, both turn signals. Any odd electrical behavior on a 452 is a SAM warning.
  11. Check the chassis underneath for rust at the rear subframe and the exhaust mounts. The Tridion cell stays clean — the subframes don't.
  12. Verify any service history you can — UK MOT history via the DVLA tool, German TÜV records, French contrôle technique. Documented turbo replacement and water-leak remediation are the two highest-value receipts on this chassis.

Full PPI walkthrough →

Accessories & aftermarket

Pre-filtered searches at the big vendors. We don't take a cut on these clicks today — if you'd rather we did, tell us.

Find accessories: Top Amazon Finds ↗ Top eBay Finds ↗ Top AliExpress Finds ↗

Where to buy parts

Region-by-region. OEM via Mercedes is always available; the alternates below are owner-vetted.

United States

  • Pelican Parts (Smart catalog) OEM and quality aftermarket. Limited 452 coverage because the chassis was never sold in the US, but worth checking — they carry M160 crossover parts that fit.
  • RockAuto Cheapest aftermarket prices when 452 parts are listed. Confirm fitment in the workshop manual first — US catalog is patchy on this chassis.

United Kingdom

  • smartmania.co.uk UK Smart specialist. Genuine + aftermarket. Strong stock for 452 service items including M160 turbo and water pump.
  • Cosmic Cabrios Roof / Cabrio specialist worldwide. The 452 Roadster cloth-top authority. Will ship internationally.
  • Mercedes-Benz UK Parts OEM via UK MB dealer network. 452 catalog availability is shrinking but major service items are still listed.
  • smart-spares.co.uk UK-based 450/451/452 breaker. Used and reconditioned parts when new is unavailable — increasingly the source for cosmetic and trim items.

European Union

  • AutoDoc Pan-European. Wide aftermarket catalog with EN/DE/FR/IT/ES/NL/PL UI. Good 452 catalog including turbo and water pump assemblies.
  • Mister-Auto France-based, ships across EU.
  • smartfreaks.de German Smart specialist. Strong on 452-specific parts and the only source for some EU-market trim items.

Australia

Find a Smart-experienced mechanic

Curated directory of 130+ shops across the US, Canada, UK, and Europe that actually work on Smarts — not just every Mercedes dealer that took the franchise. The map is owner-recommended, vetted before listing, and updated as shops open and close.

Open the Mechanic Directory →

Stuck? Ask SmartDiag-AI.

Tell SmartDiag what your Roadster (452) is doing — or paste a code. It'll work the cheap-first checks with you, weight likely causes against community-known patterns, and cite the workshop manual for each suggestion. The link below pre-fills your chassis.

Try SmartDiag-AI →

Frequently asked questions

  • Does the Roadster really leak water that badly?
    Yes. Mercedes published a 48-page guide specifically because the chassis leaks from multiple points and they wanted dealers to have a reference. The leaks are not a defect to be fixed once — they're an ongoing maintenance reality for the life of the car. Trunk drains, roof seals, windscreen surround, rear quarter panels: all eventually need attention. Owners who accept this and stay ahead of it have great cars. Owners who ignore it end up with dead SAM modules and ruined interiors. Buy with eyes open.
  • Roadster vs Roadster Coupe — which should I buy?
    Both share the chassis, drivetrain, and most of the leaks. The Coupe has a glass targa roof and is more weather-tight in everyday driving — the right choice if you want to use the car in winter or in rainy climates. The Roadster has the cloth top and the open-roadster experience but adds another set of seal-and-mechanism wear items. In the UK enthusiast market the Brabus Coupe is the most desirable variant; in warm-weather markets (southern EU, AU) the Roadster gets equal love.
  • Was the 452 ever sold in the US?
    No. The 452 was never officially imported. A handful of grey-market or DOT/EPA exemption cars have made it to the US over the years, but the volume audience is the UK, EU, Japan, and AU. Under the 25-year rule, US imports become legal starting in 2028 (for 2003 cars), with 2004–2006 cars following in 2029–2031. A steady trickle of enthusiast cars will land in the US over that decade.
  • How does the gearbox compare to the 451's?
    Same single-clutch family — 6-speed Getrag in the 452 vs 5-speed in the 451. The 452 ships with paddle shifters as standard, and most enthusiast owners drive in manual mode permanently using the paddles. That makes the gearbox far more enjoyable in the Roadster than in the Fortwo, because you have a sportscar chassis to apply the paddles to. The auto mode pauses the same way. Manual mode hides it.
  • Is the Brabus V6 BiTurbo a real car?
    Real but not production. Approximately 10 prototype cars were built — Mercedes 3.8L V6 BiTurbo from the SLK/CLK platform shoehorned into the 452's mid-engine bay, ~170 hp. Richard Hammond drove one on Top Gear and the surviving cars are well-known in the global Smart community. They were never offered for sale to the public. If someone offers you one for less than mid-six figures GBP, it's almost certainly a replica or a fraud.
  • Can I work on a 452 myself?
    Most surface jobs — oil, filters, spark plugs, brake pads, water-leak resealing — are owner-friendly. The water-leak work specifically is the kind of patient, methodical owner-doable repair the 452 community has documented thoroughly on smartroadsterforum and Evilution. The harder stuff is the turbo, the water pump, the SAM, and the gearbox internals — these sit in a tighter mid-engine bay than the 450/451 Fortwo and become Smart-experienced shop jobs.
  • Where do I buy 452 parts in 2026?
    UK: smartmania.co.uk, smart-spares.co.uk, and Cosmic Cabrios for any roof or trim work. EU: AutoDoc, Mister-Auto, and smartfreaks.de. The Mercedes UK and EU parts catalogs still list most major service items but cosmetic and trim availability is shrinking — UK and EU breakers are increasingly the source for those. For US grey-market or future 25-year-rule owners, ordering from the UK or EU is the realistic supply chain.
  • Are 452s reliable?
    For their age and rarity, mostly yes — IF you treat the water situation as ongoing maintenance and stay ahead of the M160 turbo. Owners who do these two things and drive the car in manual mode get reliable cars that last decades. Owners who treat a 452 like a normal used car (water? eventually. turbo? eventually.) end up with a dead car. The 452 rewards engaged ownership and punishes neglect more than the Fortwo chassis do.
  • Will values keep going up?
    The honest answer: 452 values have been trending up in the UK and EU as the cars become rarer and the enthusiast community grows. Brabus Coupes and Finale Edition cars in clean condition lead the market. Standard Roadsters in average condition are still affordable. Whether values keep going up depends on how the chassis ages — cars with documented water-leak remediation and turbo replacement command real premiums and that gap is widening.
  • Will smart come back as a sportscar?
    Almost certainly not. Smart in 2024+ is a Mercedes-Geely joint venture building Tesla-fighter SUVs (the #1 and #3) — completely different cars. The 452 was a one-time experiment that didn't sell well at the time and is now a cult car because of it. Treat your Roadster as a piece of automotive history.