Mercedes-Benz SLK R170 and R171 (1996 to 2011)

The SLK brought Mercedes-Benz into the compact roadster class in 1996 and did so with a party trick: the Vario-Roof, a two-piece steel folding hard top that turned a snug coupe into an open car at the press of a button. The K in the name stood for kurz, German for short, and early cars were so popular that waiting lists built up. The first generation, the R170, was built in Bremen and shared many mechanical parts with the C-Class of the time.

The second generation R171 followed in 2004 with sharper styling inspired by Mercedes' Formula One cars, more power and a more sophisticated cabin, including the optional Airscarf neck-level heating. It ran until 2011.

Neither generation is a hardcore sports car. Most are relaxed, comfortable two-seaters with automatic gearboxes, though the V6 models and the supercharged and V8 AMG versions are genuinely quick. The R170 has a reputation for rust, especially around the front wings, and both cars can suffer roof switch and water leak problems that affect the electrics. The R171 is better protected against corrosion, but its rear subframes, seven-speed automatics and some early engines need attention. Sources agree that a well maintained car with full history makes a pleasing, easy-going classic.

• R170 production: 1996 to 2004, Bremen, Germany. Hagerty quotes 311,222 built, with the 230 Kompressor the most numerous at 113,520; Classics World gives about 311,000 worldwide and around 25,000 sold in the UK.
• R171 production: 2004 to 2011. No reliable production total was found in the sources opened.
• Body style: two-seat roadster with electro-hydraulic folding steel roof.
• R170 engines: 200 (2.0, about 132bhp, not in all markets); 200 Kompressor (about 161bhp); 230 Kompressor (2.3 supercharged four, about 190 to 194bhp); 320 (3.2 V6, 215bhp); SLK 32 AMG (supercharged 3.2 V6, quoted at 344 to 349bhp).
• R171 engines: SLK 200 Kompressor (1.8 supercharged four, about 159bhp, rising to 179bhp from 2008); SLK 280 (3.0 V6, 225bhp, renamed SLK 300 in 2009); SLK 350 (3.5 V6, about 264bhp, rising to 297bhp after the facelift); SLK 55 AMG (5.4 V8, quoted at 360hp).
• R170 gearboxes: five-speed manual, six-speed manual from the 2000 facelift, five-speed automatic.
• R171 gearboxes: six-speed manual; five-speed automatic on the 200; seven-speed 7G-Tronic automatic on V6 and V8 models.

• 1996: R170 230 Kompressor launched; the only UK version at first.
• 2000: facelift with revised bumpers and body-coloured sills, six-speed manual, revised seats, standard ESP; 200 Kompressor and 320 V6 added.
• Late 2000 to 2001: SLK 32 AMG introduced.
• 2004: R171 launched as SLK 200 Kompressor and SLK 350. The V8 SLK 55 AMG also joined the range; the sources opened do not give its exact UK launch date.
• 2005: SLK 280 added.
• 2006: on the SLK 55 AMG, the front brakes change from six-piston calipers with two-piece discs to four-piston calipers with one-piece discs.
• 2008: R171 facelift with new nose and tail, new instruments, more power for the 200 and 350.
• 2009: 280 renamed 300; 2LOOK Edition.
• Special editions included Sport, Edition 10 and 200 Grand Edition.
• 2011: production ends.

Bodywork and structure

• R170: rust is the main risk. Check the front wings around the edges and behind the indicator and headlamp units, which is often worst on pre-facelift cars. Also check wheel arches, sill ends, the tops of the windscreen pillars and screen surround, floors and the rear subframe.
• Surface rust on the bonnet and boot lid from stone chips is common. Later R170s are less prone but not immune.
• R171: the galvanised body is usually rust-free, but rear subframes on older cars corrode badly enough to fail an MoT. Get a torch underneath.
• Check panel gaps for accident repair.

Engine

• 230 Kompressor: listen for supercharger whine and confirm the boost arrives smoothly. Look for oil leaks and coolant loss at the radiator or water pump.
• Oil can wick along the wiring loom and damage sensors or the engine ECU; post-facelift R170s can suffer oil contamination at an ignition timing solenoid.
• R170 V6: generally robust. AMG cars need complete, verifiable service history.
• R171: early 280 and 350 V6 engines can suffer balancer shaft gear wear; misfires and the engine warning light are warning signs. Early 200s can suffer premature timing chain and sprocket failure. Check V6 cam covers for leaks.
• SLK 55 AMG: valve cover and rear main seal leaks, and sixteen spark plugs to change.

Gearbox and drivetrain

• Manuals are tough; listen for whines and check synchromesh.
• Automatics: check for jerky or delayed changes. R170 oil cooler pipes corrode, and fluid can travel into wiring and the transmission ECU, causing limp-home mode.
• 7G-Tronic: conductor plate and valve body faults cause poor shifting and limp mode. With the car stationary and engine running, select Park and Reverse several times and feel for smooth engagement.
• Sources recommend automatic oil and filter changes around every 35,000 to 36,000 miles despite claims of sealed-for-life fluid.

Suspension, steering and brakes

• R170: corrosion at the front spring mounts; front ball joints prone to wear.
• R171: thrust arm and anti-roll bar bushes wear; broken springs are increasingly common; exhaust Y-pieces crack.
• Check brake pipes on low-use cars and confirm ABS and ESP lights come on and go out.

Electrics and interior

• Roof: it should open or close in roughly 20 to 30 seconds without hesitation. Microswitches seize if the roof is rarely used. The pump in the boot needs periodic fluid changes. Squeaky roof seals need lubricating.
• Water in the boot damages the R170's central locking pump. Lift the boot floor and spare wheel cover.
• On the R170, water near the control module, fuses and relays under the bonnet causes odd faults.
• R171: worn A-pillar and screen seals can let water reach door control modules.
• R170 rubberised trim flakes; check the Airscarf and heated seats on R171s.

Identity and paperwork

• AMG models should match their VIN and engine number. Ask a Mercedes dealer or the club to confirm the build data.
• Confirm R171 V6 badging matches the engine, as 280 and 300 cars look similar.

Parts are generally easy to find and many R170 parts are shared with the C-Class, keeping costs down. Independent Mercedes specialists are common. AMG-specific parts are dearer. Roof hydraulic repairs are often less daunting than feared once diagnosed.

The Mercedes-Benz Club (mercedes-benz-club.co.uk (opens in a new tab)) is the factory-approved UK owners' club and holds SLK events.

• Has the roof been cycled recently, and has the hydraulic fluid ever been changed?
• Has the automatic gearbox oil and filter been changed, and when?
• What rust repairs have been done, especially to front wings and the rear subframe?
• Is there evidence of water in the boot or footwells, or any central locking faults?
• For an R171 V6 or a 200, has the balancer shaft or timing chain been checked or replaced?