Mercedes SLK R170 buying guide: weak spots and which engine to choose

The SLK R170 is now one of the cheapest ways into a hardtop roadster, but cheap cars can be expensive to fix. In this guide I have collected the weak spots described in German used-car tests and owners' guides, and the differences between the engine versions. The model's history, dates and full specification table are in a separate article: Mercedes SLK R170 — history, the Vario-Roof and the engine range.

Which SLK R170 engine should you choose?

The most often recommended compromise is the SLK 230 Kompressor, and the alternative without its typical faults is the SLK 320 V6. The choice depends on how much you want to spend and how much performance matters to you.

Sources: autoscout24.at (2010), mercedesblog.com (2026), Euro Premium Parts, Wikipedia.

According to the autoscout24.at used-car test, the exhaust manifold on the SLK 230 Kompressor can crack, and the repair also requires replacing the supercharger — in 2010 this cost about €2,000. That is why the author pointed to the SLK 320 as a sensible alternative, and to the SLK 200 for those who want low running costs. Mercedesblog.com, on the other hand, considers a low-mileage SLK 230 Kompressor the most sensible compromise and notes that many pre-facelift cars have covered more than 250,000 km.

What should you check on the Vario-Roof?

The roof should open and close in about 25 seconds, smoothly and without stopping — that is the first test during an inspection. According to mercedesblog.com, if it takes noticeably longer (the author gives a threshold of about 28 seconds), there may be a leak in the hydraulic system.

The most common causes of roof faults:

• Sensors and wiring — according to auto motor und sport, these, rather than the mechanism or the pump, cause most problems. According to Euro Premium Parts, micro-switch faults are often misdiagnosed as hydraulic failures.
• Hydraulic rams — they lose their seal with age, which shows as slow or incomplete roof movement.
• The pump — it sits in the boot behind the trim on the right-hand side; it rarely fails, but can seize on cars that have stood for a long time.
• Water — autoscout24.at recommends cleaning the drains and greasing the mechanism regularly; neglect ends with water in the roof electronics, which is more common on facelifted cars.

Also check the roof seals, the mechanism joints (mercedesblog.com advises looking for rust on them) and any signs of moisture in the cabin and the boot.

Where does the SLK R170 rust?

According to auto motor und sport, corrosion and accident repairs are now the biggest weak points of the first SLK. At the same time, the magazine considers the R170 less rust-prone than other 1990s Mercedes models.

Places worth inspecting:

• the wing edges and wheel arches,
• the sills and their drains,
• the bonnet edges,
• the axle carriers (surface rust is common and easy to treat),
• the front subframe mounts — on cars driven on salted roads they can corrode more deeply,
• the exhaust system, especially the rear silencer.

What faults do the Kompressor and V6 engines have?

The R170's engines are considered durable, but after more than 20 years they show typical ancillary faults. According to the Euro Premium Parts guide and mercedesblog.com, the most common are:

• the supercharger coupling on Kompressor versions — the symptoms are a rattle at idle and loss of boost,
• the timing chain tensioner on the four-cylinder M111 — noise on start-up needs checking,
• oil leaks around the camshaft adjuster on facelifted cars,
• perishing coolant hoses on cars older than 15 years,
• plastic intake swirl flaps on the V6 (SLK 320 and 32 AMG), which can crack,
• hardening valve cover gaskets on the V6,
• the supercharger drive belt and tensioner on the SLK 32 AMG.

Manual or automatic?

The five-speed automatic suits most versions better. The autoscout24.at test describes the manual gearbox as notchy (German: "hakelig") and recommends the automatic with every engine, even though it costs a little performance and fuel. In 2001 the five-speed manual was replaced by a six-speed, and the SLK 32 AMG was offered with the automatic only.

What should you check in the interior and electrics?

The R170's interior is solid, but it has a few typical faults that add to the cost of putting a car right:

• peeling soft-touch coating on the plastics — according to autoscout24.at, more common than roof faults,
• door trims coming loose,
• auto-dimming mirrors losing their dimming function (new glass cost about €120 in 2010),
• mirror and window switches, broken seat springs and non-working backrest heating,
• dead pixels in the instrument cluster displays and comfort module problems (central locking).

Pre- or post-facelift?

Cars built after the February 2000 facelift are better equipped for safety, but have their own weaknesses. The advantages include ESP, side airbags, a larger fuel tank (53 instead of 45 litres), a six-speed manual from 2001, and the SLK 200 Kompressor and SLK 320 engines. On the other hand, according to autoscout24.at, the roof electronics are more often flooded on facelifted cars, and mercedesblog.com points to oil leaks at the camshaft adjuster.

How much does an SLK R170 cost?

Asking prices depend mainly on the engine, mileage and service history. According to a review of listings published by mercedesblog.com in May 2026:

• pre-facelift naturally aspirated SLK 200 — from about €1,000,
• pre-facelift SLK 230 Kompressor — from about €1,500, usually with more than 250,000 km,
• SLK 230 Kompressor with under 150,000 km — about €5,000,
• most SLK 200 and 230 Kompressor offers — €5,000–7,000,
• well-kept V6 — up to about €20,000, SLK 32 AMG — about €20,000–25,000.

For comparison, in April 2019 auto motor und sport reported that well-kept four-cylinder cars with about 100,000 km cost from €5,000, and good V6 cars at least €9,000. These are mostly asking prices rather than transaction prices, so treat them as a rough range.

How do you inspect an SLK R170 step by step?

It is best to start with the roof and the paperwork, and finish with a test drive on a warm engine:

1. Open and close the roof several times, timing it; check that it does not stop halfway and that no error messages appear.
2. Inspect the boot and cabin for moisture, water marks and a musty smell.
3. Check the sills, wheel arches, wing edges and the underside on a lift.
4. Compare the panel gaps and paint thickness — look for signs of accident repairs.
5. Listen to the engine from cold (timing chain tensioner) and warm (supercharger rattle, exhaust manifold leaks).
6. Check the switches, seats, seat heating and instrument cluster.
7. Ask for the service history and invoices for roof repairs.

If you are comparing the SLK with other roadsters, read the Jaguar XJS vs Mercedes SL comparison. A larger Mercedes roadster from the same era, the 1998 SL500, is in the showroom, and the other cars are on the Buy a classic page. More buying guides are in the Buying and inspection category.