Buying Guide Mercedes-Benz SLK R170

Asparkling two-seater with an effective folding hard–top and a prestigious badge was bound to sell well. The first Mercedes SLK certainly did. Twenty years on from launch, a glut of cars on the used market means a tatty, high-mileage example can be had for less than £1500. Models range from the supercharged 200 to the thunderous 354bhp 32 AMG.

This month’s experts are David Thompson (0131 661 4815), whose Edinburgh workshop has a long history of working on all Mercedes from the Sixties to the present day, Martin Lalor, of independent Mercedes specialist RPL in Hampshire (, 01420 479477) and Gordon Newport from Berkshirebased independent Mercedes specialist Automerc (, 01635 551551).

Which one to choose?

Mercedes-Benz SLK 230 Kompressor R170 The new small sports–roadster Mercedes launched in 1996 was based on the 1994 C-class W202, and the M111 supercharged DOHC four–cylinder engine was good for 193bhp. Like all SLKs, they came with the folding hard–top ‘Vario Roof’ that combines saloon–like security with true open–topped freedom. Most were five–speed automatics but five–speed manuals were offered too. It’s thought as many as nine out of ten SLKs sold in the UK were 230Ks. The SLK’s February 2000 facelift brought with it body–coloured side skirts, a six–speed manual gearbox option and flatter cornering. All facelifted SLKs also have standard traction control, an improved ride and better seats.

Mercedes-Benz SLK 200 Kompressor R170 The smaller–engined 200K, launched in 2000, is slightly less brisk than the 230K but remains in the same road tax band K. It’s also marginally more economical. SLK 320. Smooth V6, built from 2000-04, sounds terrific and works well with both six–speed manual and auto transmission but isn’t much quicker than 230K and loses 4-6mpg overall. Nonetheless, it’s becoming the sought–after version for the more grown–up engine and relative exclusivity.

Mercedes-Benz SLK 32 AMG R170 A hand-built 349bhp V6 and many special AMG goodies transformed the SLK (2001-2004) into a road rocket. Never sold in the quantities of the later SLK 55 AMG and now hard to find.

Folding roof The Vario Roof doesn’t take kindly to neglect. ‘People leave them up over winter and then expect them to work perfectly when the sun comes out,’ says David Thompson. Troubles vary from stiff hinges and squeaky seals – both curable with a bit of DIY lubrication – to failed roof pumps, which cost £800 to replace. Raise and lower the roof several times with the engine running and listen for noises or hesitation. It should go up and down smoothly in about 24 seconds. Both windows should lower automatically when the roof starts to open and rise again after the roof is closed.

Some problems are caused by failed microswitches in the roof and bootlid; there are nine in all and while it’s unusual for more than one to fail at once, it’s hard to predict the cost of labour for investigating and replacing a £25 part. The system uses small actuating cylinders in the roof, a pump concealed in the right–hand side of the boot and two rams that raise and lower the bootlid. Stains or droops in the headlining may be just down to water ingress but could also be signs of leaking cylinders. It’s best to walk away from anything that doesn’t work perfectly – there are so many to choose from that rescuing a sickly example is illogical unless the price is particularly low. Damp boot carpets or signs of condensation are probably due to water ingress created by a blocked drain hole, which is easy to fix.

Engine and transmission The R170 may be cheap to buy but it’s still a Mercedes and can be costly to service through a main dealer. An ‘A’ service is around £400 while the more involved ‘B’ service is nearer £800, though independents charge less than half this amount. Check which is due, and how soon, before you make an offer. Bear in mind that V6s have 12 spark plugs, which cost a whopping £16 each.

‘The most common problems on four–cylinder cars are clogged flame traps and damaged air–mass meters,’ says Martin Lalor. ‘This usually causes the engine management light to come on but may just show up as a lack of power.’

The air–mass meter (also known as mass air-flow or MAF sensor) can be cleaned or replaced as a relatively easy and inexpensive DIY job but to be sure there’s nothing more serious amiss, specialist garages can perform a diagnostic plug–in to reveal fault codes. Basic onboard diagnostic readers are widely available online from £10 and you can buy adaptor cables to convert the Mercedes 38-pin sockets (located in the engine bay pre-2000, by the bonnet release lever post-2000) into compatible 16-pin connections for another £4.

An engine that shakes when idling needs new mounts (£200 fitted). Listen out for loud or continuous noises from a Kompressor’s supercharger – a good used one costs £200-£250, plus the same again in labour.

Four-cylinder engines have a magnet that adjusts camshaft timing. Find it on the right of the front face of the cylinder head, held on with three hex–head bolts. Oil can leak from the head into the magnet, thence into the plug mounted on it and in bad cases all the way up the loom to the engine or gearbox ECU, finishing it off and landing you with a £1000 bill. Unclip the plug to the magnet and check for oil inside. Replacing the magnet (£100 fitted) and a revised, oil–proof portion of the loom called a starter line (£18) is good insurance.

V6s have fewer vices but the exhaust system features four catalytic converters in two pipes, which cost £400-£500 to replace. Misbehaviour from an automatic gearbox – being stuck in gear, for example – can often be traced to a failed speed sensor, faulty multi-pin connector or even something as simple as low transmission fluid, but don’t assume anything is cheap to fix until it’s been professionally assessed and diagnosed.

Bodywork Most Mercedes of this generation will have exhibited varying degrees of corrosion problems by now. The question is how well – or otherwise – they have been repaired. On the R170 you should look closely at the rear arches – feel inside, especially if there are rust scabs visible from the outside. Front arches can bloom just as badly, as can the bootlid around the keyhole and – more seriously – the sills and floors. Walk away from anything with evidence of rot underneath but more judgement is required with resprayed cars.

Some SLKs will already have been repainted to correct cosmetic problems caused by rust. It’s vital to distinguish between a hasty wipe of filler and a blowover, and a professional de-rusting and refinishing job. Photos of the process and a bill in the history file are encouraging – a full respray in the original colour can cost anything between £1500 and £4000 – while overspray on light lenses, tyres, parts of the engine bay, trim or side-skirts is more of a worry. Look along each side of the car and check for dips, ripples and dull patches in the paint. Poorly repaired rust–spots will bubble up again in months.

Interior The large centre console suffers from peeling paint around the handbrake area and the top surface where the seatbelt buckles constantly abrade them. Handles and door cards are affected too. The plastic underneath is black – it’s not so much of a problem if the top paint is also black, but looks shabby and unpleasant on cars with grey, blue, red or especially cream interiors. Advice and instructions on removing and repainting the console abound on Mercedes forums like, so use it as a bargaining chip if it’s the only major failing on an otherwise good car.

Secondly, seats wear surprisingly easily, and this shows up particularly badly on those finished in pale colours. You can view this as a warning sign of hard use and/or an uncaring previous owner or simply another reason to make a low offer – good used seats are readily available from online breakers from £120 a pair, often with matching door cards thrown into the deal.

Suspension and wheels Front lower balljoints fail, leading to clunks when negotiating bumps or potholes but they’re cheap to replace (at £40 each), while rear springs (from £150 per pair, fitted) have a habit of snapping off the bottom coil – feel for thumps and bangs from each corner of the car. A persistent squeak from the rear is more likely to be dried-out bushes; budget around £200 to fix.

Alloy wheels blister and bubble – they cost £250-£300 to refurbish and up to £400 to replace.

What to pay

You can get a 230K for £1500 but it will probably be nasty.

Budget £2500-£3000 for a good one with full history and 60k-70k miles.

The 200K is so close to the 230K in everyday use that prices are about the same, although condition matters more than specification.

The 320 commands a premium over four-cylinder cars, so prices start at £3000, with later low-mileage cars £5000-£6000.

320 AMGs are rare and already appreciating in value. Expect to pay £10,000-£15,000.

“Walk away from anything whose Vario Roof doesn’t work properly – rescuing a sickly example is illogical”

Mercedes build quality and anticorrosion protection took a nosedive during this era, so poor body repairs and cheap resprays are the main concerns.

“It’s vital to distinguish between a hasty wipe of filler and a blow-over, and a professional job”

V6 isn’t much quicker than a 230K and a new set of plugs costs over £190 – but it’s creamy-smooth and sounds terrific.

Centre console suffers from peeling paint but there’s plenty of guidance online on how to rectify it. Used seats cost £120 a pair.

SLK’s bootlid tilts back automatically when the folding metal Vario Roof is deployed, but the complex folding system suffers from lack of use.

Owning an SLK

Martin Davies Redhill

Surrey Martin did his research thoroughly before buying the SLK in our pictures, settling on what he regards as the sweet spot of the range – an SLK 320. ‘You get the V6 power and sound and there’s no supercharger, so that’s one less major ancillary to go wrong.,’ he says. ‘Many owners do some or all of their own work, as there’s a wealth of knowledge on the forums that can save a lot of money.

‘I see no point in using a dealership with a car this old except as a source of parts for one of the independent specialists to fit. I’ve modified the tray at the top of the dashboard on mine to power and support a satnav and phone. I’ve also changed the head unit and added Bluetooth and I’ll be looking to upgrade the speakers too.

‘But the best thing is still the sense of involvement… you get to feel a part of the car when you’re driving. The ability to lower the roof on a whim – even in cold weather as the heating on the car is superb – is terrific and of course you get to enjoy the sound of that engine.’

James Wilson Glasgow

An American adrift in Glasgow, James Wilson has two British sports cars – a Rochdale Olympic and a Jensen-Healey – and considered an MG TF and a Lotus Elise before settling on an SLK in spring this year. ‘I wanted a modern classic and the Mercedes seemed to fit the bill,’ he says. ‘I love the folding hardtop, which was pretty much the first mass–produced system that really worked properly and sold widely. But it was the reliability that swung it for me. I wasn’t looking solely at the V6 cars but I didn’t want a silver one, and having joined the online forum at slkworld. com I asked for advice, and someone put me on to a black car for sale in York.

‘I ended up buying a 15-year-old SLK 320 with full history and 32,000 miles. It was really well looked after, so it practically felt like a new car once I’d had the wheels refurbished and made corrections to two small areas of paint. ‘I sometimes think it’s a little crazy to have heated seats in a sports car, but it’s more sports–luxury than out–and–out performance. I like it a lot!’

Mark Appleby Watford, Hertfordshire

‘For me, the best thing about my SLK 230K is putting the roof down on a summer’s day – the hot air trapped inside the car disappears instantly and you can enjoy the sound of the engine,’ says Mark Appleby. He reckons it’s easy to service an SLK at home, especially with wisdom imparted from the various forums, and is proving this by repairing a tatty SLK 320 he recently bought as a non–runner.

‘It’s got four rusty wheelarches and the alloy wheels are in bad shape, but I reckon I’ll get it looking better this summer. The SLK does have a few shortcomings – the remote central locking gets used all the time but when it fails, the keyhole part of the mechanism is untouched and seizes up, making it a struggle to turn the key. Also, the aerial is located behind the rear bumper and the whole car can shield the radio signal.

‘You find a lot of minor issues with these cars but you don’t need to know much to get around them – people on the forums will talk you through just about any job. The bottom line is that it’s smooth, handles well and is so much fun for the money.

1998 Mercedes-Benz SLK R170 230 £3500

Full body respray (£2000) in 2015 by a local classic car restoration company. At the time of the respray it was de– badged and the bumpers, trim, wheels and door handles were all colour-coded. There is a DAB Bluetooth CD radio player with hands–free capability. The throttle body and MAF sensor have also been replaced by a Mercedes–trained technician. Private plate included in sale.

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