Mercedes-Benz SLK problems, reliability and years to avoid
If you are considering buying a used Mercedes-Benz SLK, these are the common problems worth knowing about first. Our garage database tracks 7 known faults for this model, 4 of them rated high severity. Every one below is a repair bill a seller has good reason not to mention.
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Is the Mercedes-Benz SLK reliable?
The Mercedes-Benz SLK has 7 known faults in our database across 2 generations, 4 of them rated high severity. The most serious are electrics (failure of the complex folding hardtop roof and window mechanism) and engine (soft metal on the timing chain sprocket that drives the balance shaft on the M272 V6). None of them makes the car a bad buy on its own; the risk is a seller who knows and says nothing.
That is a count of the faults we hold, not a reliability score. Popular cars get written about more, and a newer generation has had less time to show its faults.
Which Mercedes-Benz SLK years should you avoid?
No year is a write-off on its own. What matters is which serious faults a given year and engine can have, and whether the car in front of you has had them fixed.
R170, 1996 to 20043 high severity
5 known faults, the serious ones in the electrics, engine
R172, 2011 to 20151 high severity
2 known faults, the serious ones in the bodywork and trim
Years and engines with a serious known fault
1996 to 2004, All R170 models: failure of the complex folding hardtop roof and window mechanism
2004 to 2008, V6 petrol (M272: C 230/280/350, E 280/350, SLK 280/300/350, ML 350) / V8 petrol (M273: E 500 from 2006 and ML 500 from the 2008 model year; not fitted to the SLK, whose SLK 55 AMG uses the M113): soft metal on the timing chain sprocket that drives the balance shaft
2002 to 2013, 1.8 Kompressor / CGI Petrol (M271): single-row timing chain stretches and jumps teeth, destroying the valves
2011 to 2013, All R172 models with specific roof material: the colour-coded roof panels on either side of the glass roof can delaminate
Each one is set out in full below, with the symptoms, the typical mileage and a rough repair cost.
Generation 1 of 25 known faults · 10 owner reports · 18 good notes
Mercedes-Benz SLK R170 (1996 to 2004) problems
Engine/EmissionsHigh severity📝 Editorial
Soft metal on the timing chain sprocket that drives the balance shaft on the M272 V6 (and the matching idler gear on the M273 V8) wears away, the camshaft timing drifts and eventually the engine timing is destroyed. It was covered by a manufacturer technical bulletin. One owner paid 2,000 pounds for a balance shaft on a 2005 CLK 350, and another car needed a timing repair and then a balance shaft within months.
Rough guide
£2000-4000
Typical symptoms
Engine Management Light (EML) on
fault codes P0016 / P0017 (camshaft timing)
rough running or misfiring
Affected vehicles
Engines:
V6 petrol (M272: C 230/280/350, E 280/350, SLK 280/300/350, ML 350) / V8 petrol (M273: E 500 from 2006 and ML 500 from the 2008 model year; not fitted to the SLK, whose SLK 55 AMG uses the M113)
Typical mileage:
60000-90000 miles
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Engine/EmissionsHigh severity📝 Editorial
Single-row timing chain stretches and jumps teeth, destroying the valves
Rough guide
£1500-2500
Typical symptoms
loud metallic rattle on startup for 3-5 seconds
engine management light
loss of compression and non-start
Affected vehicles
Engines:
1.8 Kompressor / CGI Petrol (M271)
Typical mileage:
60000-90000 miles
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OtherMedium severity💬 3 owner reports, 2014
Severe corrosion, particularly affecting wheel arches, door handles, and boot lid. This is a common issue across Mercedes models from this era.
Rough guide
£500-1500+
Typical symptoms
Visible rust bubbles on wheel arches
Corrosion around door handles
Rust on boot lid edges
Affected vehicles
Engines:
All R170 models
Typical mileage:
70000-120000 miles
🔍 We have a specific pre-purchase check for this faultCheck an advert →
ElectricalHigh severity💬 3 owner reports, 2014
Failure of the complex folding hardtop roof and window mechanism, often due to sensor issues or hydraulic pump failure. Repairs can be prohibitively expensive on older cars.
Rough guide
£1000-3000+
Typical symptoms
Roof fails to open or close fully
Windows do not drop or raise correctly during roof operation
Roof mechanism jams or makes unusual noises
Affected vehicles
Engines:
All R170 models
Typical mileage:
60000-100000 miles
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Engine/EmissionsMedium severity📝 Editorial
Failure of the right-side pre-catalytic converters and main catalytic converters is common on the SLK320 V6. Mercedes main dealer replacement costs are very high.
Rough guide
£1400-2000
Typical symptoms
Reduced engine performance
Check engine light illuminated
Rattling noise from exhaust system
Failed MOT emissions test
Affected vehicles
Engines:
3.2 V6 (SLK320) petrol
Typical mileage:
80000-120000 miles
🔍 We have a specific pre-purchase check for this faultCheck an advert →
What owners report on the R170
10 single reports, unconfirmed
One owner each, in their own words rewritten as a line, and not counted in our risk scoring. A fault joins the list above once a second report or an editorial source backs it.
Bodywork · June 2017Lacquer peeled from the metallic red paint on a 2010 SLK 200K, which was found to have been poorly resprayed previously.
Suspension and steering · March 2017A 2005 SLK350 experienced multiple spring and damper failures by 68,000 miles, including a broken front coil spring.
Gearbox and clutch · April 2015A 2009 SLK200 with 40,000 miles developed a grinding noise from the rear differential, with metal shards found in the oil.
Interior · April 2015A centre console lid that would not open on both sides was fixed by enlarging the holes for the locking pins.
Gearbox and clutch · March 2014The gear linkage on a 2009 SLK 200K manual with 17,000 miles failed due to a missing circlip, with repair costs quoted.
Electrics · October 2013Blocked bulkhead vent drains on a 2008 SLK caused rainwater to flood the heater motor, costing £800 to repair.
Gearbox and clutch · May 2013The clutch slave cylinder on a manual model is located inside the bellhousing, making its replacement a costly labour job of around £500.
Electrics · November 2012A 2006 SLK350 with 49,000 miles had numerous electrical faults, including a stuck driver's window and transmission issues, costing over £3,000.
Interior · October 2012The air conditioning compressor on a 2005 SLK failed at 40,000 miles, with a replacement cost of £1,600.
Bodywork · February 2012This car experienced water ingress through its roof and boot lid sealing components.
What owners like about the R170
18 notes
This model received a strong four-star rating for occupant protection in 2002 NCAP assessments.
Mercedes recorded the fifth lowest average expenditure on warranty claims for cars up to ten years old in 2002.
The model generally had the ninth lowest average warranty repair costs in the 2003 Warranty Direct Reliability index.
Fewest problems and faults were reported, with an average number of breakdowns in a 2003 Which survey.
This model earned a four-star crash safety rating in 2002 NCAP tests, with low warranty claim expenses.
The second-generation SLK is a desirable car with a folding hardtop, offering a more practical and liveable experience than some rivals.
The facelifted model features 650 new parts, including updated styling, a modified interior, and more economical engines with increased output.
The new NTG 2.5 audio and telematics system is user-friendly, offering Bluetooth hands-free and a media interface for mobile devices.
The 305PS SLK350 automatic model now produces under 225g/km of CO2 emissions.
The SLK 350 engine offers increased power and torque, with the 7G-TRONIC automatic transmission providing automatic throttle blipping on downshifts.
The four-cylinder supercharged engine was boosted to 184 hp, with torque increased to 250 Nm, while reducing fuel consumption and CO2 emissions.
The SLK 55 AMG is equipped with a 5.5-litre V8 engine producing 360 hp and 510 Nm of torque.
New SLK models feature a precise six-speed manual gearbox as standard, with automatic transmissions available as options.
A newly developed direct steering system, available as an option, enhances agility and manoeuvrability while maintaining high-speed stability.
The direct-steer system uses a new rack with slick gearing, reducing steering wheel revolutions from lock to lock by about 25 percent.
The 2008 SLK 55 AMG features sharpened handling dynamics and new direct steering with variable servo assistance for improved agility.
The improved SLK350 manual, available from April 2007, offers good acceleration, pleasing sound, and feels secure when driven quickly.
The SLK 2LOOK Edition, launched June 2009, features distinctive paint options, 18-inch alloy wheels, and a luxurious black and white leather interior.
Generation 2 of 22 known faults · 3 owner reports · 3 good notes
Mercedes-Benz SLK R172 (2011 to 2015) problems
OtherMedium severity💬 6 owner reports, 2015 to 2017
Widespread problem with microblistering and peeling lacquer on Mars Red and Fire Opal Red paint finishes, particularly on cars built between 2011 and 2015. This often requires a full bare-metal respray.
Rough guide
£2000-4000+
Typical symptoms
Tiny paint blisters appearing all over the bodywork
Peeling lacquer, especially on bumper valances
Blistering worse at low temperatures, disappearing when hot
Affected vehicles
Engines:
Mars Red / Fire Opal Red paint finishes
Typical mileage:
10000-50000 miles
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OtherHigh severity💬 3 owner reports, 2018 to 2020
The colour-coded roof panels on either side of the glass roof can delaminate, allowing water to enter under the roof and leak into the cabin, soaking seats and carpets. This roof material was reportedly discontinued in 2013 due to this problem.
Rough guide
£600-1000+
Typical symptoms
Water puddles on seats or soaked carpets
Damp interior smell
Visible delamination or bowing of roof panels in hot weather
Roof 'coming away at the back in sunshine'
Affected vehicles
Engines:
All R172 models with specific roof material
Typical mileage:
30000-80000 miles
🔍 We have a specific pre-purchase check for this faultCheck an advert →
What owners report on the R172
3 single reports, unconfirmed
One owner each, in their own words rewritten as a line, and not counted in our risk scoring. A fault joins the list above once a second report or an editorial source backs it.
Electrics · April 2017A 2013 SLK350 with 19,700 miles experienced multiple electrical problems, including new RPM and NOX sensors, a heater box, and an aerial.
Electrics · March 2017The driver's door lock of a 2013 SLK AMG became stuck, with the dealer attempting to charge for a diagnostic despite warranty coverage.
Bodywork · February 2017A 2013 Mercedes SLK purchased in 2016 had paint problems, with the dealer offering a respray or replacement, but not a like-for-like exchange.
What owners like about the R172
3 notes
A broad range of engines are available, including a turbodiesel, all of which can be paired with Mercedes' excellent seven-speed automatic gearbox.
The SLK is well-suited for grand touring due to its comfortable ride and relaxed nature, with a quick-folding metal roof.
The SLK includes a comprehensive list of standard safety equipment, with additional options available to enhance protection.
Sellers rarely admit these faults outright
We track 21 specific phrases sellers use in adverts to soft-pedal these exact issues. Paste any Mercedes-Benz SLK advert and we check it in seconds.
Recall work is done by the manufacturer, and GOV.UK says you will not usually have to pay for it. These are the 9 DVSA recalls for the SLK, newest first. They do not tell you whether this particular car has had the work: for that, put the registration into the free GOV.UK MOT history check, which shows a recall status where the manufacturer shares it, or ask a franchised dealer to check the VIN.
🏛️ August 2021Cars built August 2004 to December 2013
The driver's air bag may have a chemical change to its propellant over time
The driver's airbag may have a chemical change to its propellant over time.
Put right by: Replace the drivers airbag.
DVSA R/2021/277108,486 vehicles affected in the UK
🏛️ August 2021Cars built August 2004 to December 2013
The driver's air bag may have a chemical change to its propellant over time
The driver's airbag may have a chemical change to its propellant over time.
Put right by: Replace the drivers airbag
DVSA R/2021/27961 vehicles affected in the UK
🏛️ March 2021Cars built February 2017 to March 2020
The software of certain communication modules may not meet specifications
The software of certain communication modules may not meet specifications.
Put right by: Carry out an update to the software of the communication module on affected vehicles.
DVSA R/2021/08336 vehicles affected in the UK
🏛️ October 2020Cars built November 2011 to May 2018
Engine control unit software to be updated
Improve the vehicle emissions via software updates.
Put right by: Update the relevant control units software and if necessary replace the NOx sensors.
DVSA R/2020/243994 vehicles affected in the UK
🏛️ February 2020Cars built June 2015 to August 2017
Emission output requires improvement
Emission output requires improvement
Put right by: Update software in the engine control unit and replace the NOx sensor if required.
DVSA R/2020/0115,255 vehicles affected in the UK
🏛️ June 2017Cars built June 2015 to January 2017
Brakes may overheat creating a risk of smoke and/or fire
The software for the Electronic Stability Program (ESP) is faulty. The fault could lead to a low residual pressure in the hydraulic system so the brakes are applied and gain heat. This increased heat will apply the brakes further and could adversely affect the brake fluid. Fire in the wheel housing cannot be ruled out.
Put right by: Recall the vehicles that are likely to be affected and update the software for the ESP.
DVSA R/2017/1576,460 vehicles affected in the UK
🏛️ April 2017Cars built January 2004 to March 2017
Faulty control unit may cause vehicle to perform outside specification
Where a control unit coding was updated in a workshop between 3 December 2016 and 5 December 2016 the coding may not correspond to the specification and may trigger unplanned action in the vehicle. The safety and emissions systems may not react as design intent.
Put right by: Recall the vehicles that are likely to be affected and update the software in the corresponding control units.
DVSA R/2017/12442 vehicles affected in the UK
🏛️ June 2016Cars built January 2016 to March 2016
Steering efficiency may be reduced
A lock nut on a rear suspension tie rod may not have been manufactured to the correct specification. It may not act as intended even tightened to specification. It is unlikely the rod will disconnect but it may loosen and affect the vehicle's handling characteristics.
Put right by: On affected vehicles replace the rear tie rod lock nuts.
DVSA R/2016/120812 vehicles affected in the UK
🏛️ May 2016Cars built February 2015 to September 2015
Electrical fault could allow vehicle to roll away when left parked
On certain vehicles fitted with 9 speed transmission the back up battery may not connect during main battery failure. This may prevent selection of Park on the transmission or operation of the electronic parking brake.
Put right by: On affected vehicles adapt harness to manufacturer's specification and recode the system.
DVSA R/2016/093717 vehicles affected in the UK
Recall data published by the Driver and Vehicle Standards Agency under the Open Government Licence v3.0. A recall listed here may not apply to every car of this model: the build dates and the registration check are what decide it.
Mercedes-Benz SLK timing chain, and service intervals
A timing chain has no change interval, which is not the same as lasting for ever. Listen for it on a used SLK, and check the oil has been changed on time. These are the figures UK specialists work to.
Timing chainChain
W203, W204, W211, 1.8 KOMPRESSOR, M271
No fixed replacement interval
Single-row timing chain notoriously stretches, jumping teeth and destroying the engine. Listen for 3-5 second metallic rattle on cold start. Often replaced between 60k-90k miles.
Automatic gearbox oil
7G-TRONIC, 722.9, 7 SPEED
40,000 miles or 4 years, whichever comes first
Mercedes initially claimed 'filled for life', which specialists call marketing over engineering. The recommendation is a fluid and filter change every 40,000 miles to prevent conductor plate failure, a GBP 800-1,200 repair. Some sources suggest 60,000 miles, so the shorter figure is recorded.
Automatic gearbox oil
722.6, 5G-TRONIC, 5 SPEED
40,000 miles
Officially 'sealed for life' but independent specialists recommend ATF (MB 236.14 spec, which supersedes 236.10 and 236.12) and filter changes every 40,000 miles to head off valve body and conductor plate trouble. Capacity is about 7.5 litres. Fitted to most pre-2011 rear-wheel-drive Mercedes including the pre-2010 C, E and SLK.
Always confirm against the vehicle handbook. Intervals vary by engine, and several manufacturers revised theirs after failures in service.
Repair costs are typical UK ranges, not quotes. Actual cost depends on condition and garage.Data last verified: September 2026
Mercedes-Benz SLK buying questions
What are the most common Mercedes-Benz SLK problems?
Three stand out. Electrics: failure of the complex folding hardtop roof and window mechanism (typically 60000 to 100000 miles). Engine: soft metal on the timing chain sprocket that drives the balance shaft on the M272 V6 (typically 60000 to 90000 miles). Engine: single-row timing chain stretches and jumps teeth, destroying the valves (typically 60000 to 90000 miles). The full list above is grouped by generation, with typical mileage and a rough repair cost for each.
Which Mercedes-Benz SLK years should I avoid?
No Mercedes-Benz SLK year is a write-off, but the R170 (1996 to 2004) carries the most serious faults: electrics and engine. The R172 (2011 to 2015) has high-severity faults on record too. Year matters less than whether the specific car has had the known fixes, so check the history for them.
What should I check when viewing a used Mercedes-Benz SLK?
Ask the seller about the electrics and engine faults on this page and whether they have been fixed, with invoices. On the test drive watch for roof fails to open or close fully, engine Management Light (EML) on and loud metallic rattle on startup for 3-5 seconds. Read the MOT history for repeat advisories, then paste the advert into the free check, which reads it against all 7 known faults before you travel. Check a Mercedes-Benz SLK advert →
Are there any recalls on the Mercedes-Benz SLK?
The DVSA lists 9 safety recalls for the Mercedes-Benz SLK issued between 2016 and 2021. The most recent, from August 2021, is "The driver's air bag may have a chemical change to its propellant over time". Recall work is done by the manufacturer, and GOV.UK says you will not usually have to pay for it. This list is by model, so it cannot tell you whether one particular car has had the work: the free GOV.UK MOT history check shows a recall status from the registration where the manufacturer shares it, and a franchised dealer can check the VIN.
What is the real MPG of a Mercedes-Benz SLK?
Owners report 35.0 mpg on average across the Mercedes-Benz SLK engines with data, about 86% of the official combined figure. The gap between official and real-world economy varies a lot by engine, so the Real MPG page lists every engine and generation separately, from 518 owner submissions. Mercedes-Benz SLK Real MPG by engine →
Where this Mercedes-Benz SLK fault data comes from
If you used to check the Honest John “Good & Bad” section before the site closed in 2026, this page is where that information now lives. We rebuilt the Mercedes-Benz SLK owner-report history from the archived Honest John dataset, added our own research, specialist and owner-club sources and DVSA recall data, and we keep it free. Each fault above is badged with its source. The same data feeds our free advert check, which reads a listing against every known fault for the exact engine and year.
Knowing what a Mercedes-Benz SLK goes wrong with is half of it. The rest is reading the advert and checking the car's history before you hand any money over.