Mercedes Benz SLK 200 CDI Engine ReplacementCompare Prices & Get Quotes
Get quotes today from trusted UK Mercedes Benz SLK 200 CDI engine specialists. Compare prices on reconditioned, rebuilt and used engines for the 2.1-litre OM646 and OM651 diesel - supply & fit available nationwide.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
From £1,800 to £3,600
Used from £900 · Reconditioned from £1,800 · Common codes: OM646.980, OM651.980
From £900
Tested, bare/short engine
From £1,800
Rod bearings addressed, tested
From quote
Upgraded bearings, full teardown, revised valvetrain
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3 Simple Steps3 Simple Stepsto Finding the Best Mercedes Benz SLK 200 CDI Replacement Engineto Finding the Best Mercedes Benz SLK 200 CDI Replacement Engine
Most replacements completed within 3-5 days.
Variant HistoryMercedes Benz SLK 200 CDI - Engine History & Specs at a Glance
The SLK 200 CDI joined the R171 generation in 2004 as Mercedes' first diesel-powered roadster, powered by the OM646 2.1-litre inline-four diesel - a refined common-rail unit delivering strong economy and relaxed cruising. In 2011, the R172 generation introduced the updated OM651 2.1-litre diesel with improved efficiency and lower emissions. These diesel SLKs offered UK owners the perfect blend of open-top motoring and excellent fuel economy, making them popular daily drivers.
Variant HistoryMercedes Benz SLK 200 CDI - Engine History & Specs at a Glance
The SLK 200 CDI joined the R171 generation in 2004 as Mercedes' first diesel-powered roadster, powered by the OM646 2.1-litre inline-four diesel - a refined common-rail unit delivering strong economy and relaxed cruising. In 2011, the R172 generation introduced the updated OM651 2.1-litre diesel with improved efficiency and lower emissions. These diesel SLKs offered UK owners the perfect blend of open-top motoring and excellent fuel economy, making them popular daily drivers.
Mercedes Benz SLK 200 CDI
Fuel TypeDiesel (common-rail turbo diesel)
Engine Size2.1L (2,148cc)
Power Output Range122-143hp across the variant's historyEngine History Timeline
OM646.980 2.1L inline-four turbo diesel, 122hp @ 4,200rpm (SLK 200 CDI, R171 launch)
OM646.980 EVO 2.1L inline-four turbo diesel, 136hp @ 4,200rpm (R171 update)
OM651.980 2.1L inline-four turbo diesel, 143hp @ 4,200rpm (SLK 200 CDI, R172 launch)
End of R172 production; SLK renamed SLC
Key Specs Snapshot
Fuel TypeDiesel (common-rail turbo diesel)Engine Size2.1L (2,148cc)Power Output Range122-143hp across the variant's historyYears Produced2004-2015Every engine fitted to the Mercedes Benz SLK 200 CDI is covered below, with UK rebuilt pricing and known failure points - from OM646 swirl flap actuator failure to OM651 timing chain tensioner wear and DPF regeneration issues.
Mercedes Benz SLK 200 CDI Engine Codes - Specifications & Replacement CostMercedes Benz SLK 200 CDI Engine Codes - Specifications & Replacement Cost
2.1L Turbo Diesel (2004-2010)
Power Output122 hp (90 kW) @ 4,200 rpm; later EVO variant: 136 hp (100 kW) @ 4,200 rpmTorque270-300 Nm @ 1,600-2,600 rpmYears Fitted2004-2010Displacement2,148ccCylindersInline 4, turbocharged with common-rail injection, Euro 4 compliantEngine CodeOM 646 DE 22 LA / 646.980
Compatible Trim Levels
- SLK 200 CDI
- SLK 200 CDI Sport (R171)
Find your exact engine code, specs and UK replacement cost guide.
Used
Tested, ready-to-fit engine
£900-£1,600
Reconditioned
Addressed known issues, tested
£1,800-£2,700
Rebuilt
Full teardown, upgraded internals
£2,000-£3,200
Common Failure
Swirl flap actuator failure and vacuum line cracks - a well-documented issue on the OM646 engine. The plastic swirl flap linkages can wear, causing rough running, loss of power and check engine lights. DPF regeneration issues are common on short-journey urban driving patterns. Injector copper seal leaks causing combustion gas escape are also reported.
The SLK 200 CDI's OM646 and OM651 diesel engines are efficient and robust, but both have well-documented weaknesses that become more pronounced with age and mileage. The OM646 suffers from swirl flap actuator failure and DPF regeneration issues, while the OM651 is prone to timing chain tensioner wear and oil cooler seal leaks. Every rebuilt engine supplied through EnginesMarket includes upgraded components addressing these original failure points, plus a minimum 12-month unlimited-mileage warranty.
The R171 Diesel's Driveability Issue
Affected Vehicles
Mercedes SLK 200 CDI (OM646.980, 2004-2010)
Typical Failure Mileage
60,000-100,000 miles
Root Cause
The OM646's swirl flap linkages are made of plastic and can wear or break over time, causing the actuator to fail. This leads to rough running, loss of power and check engine lights. The vacuum lines that operate the swirl flaps can also crack with age, causing similar symptoms.
Why It Happens
The OM646's swirl flap linkages are made of plastic and can wear or break over time, causing the actuator to fail. This leads to rough running, loss of power and check engine lights. The vacuum lines that operate the swirl flaps can also crack with age, causing similar symptoms.
Dealer (parts + labour)
£300-£600
Specialist (parts + labour)
£200-£400
What it involves
Repair or replace broken swirl flap linkages, clean intake manifold
Suitability
If caught before actuator fails
1 - 2 daysDealer (parts + labour)
£500-£900
Specialist (parts + labour)
£350-£650
What it involves
Replace swirl flap actuator, inspect vacuum lines, clear fault codes
Suitability
If actuator has failed
1 - 2 daysDealer (parts + labour)
£4,000-£5,500
Specialist (parts + labour)
£2,000-£3,200
What it involves
Complete engine swap with new intake manifold components, 12-month warranty
Suitability
If swirl flap failure has caused engine damage
1 - 2 daysAll prices are indicative UK market ranges based on current UK specialist supplier data.| Repair Tier | Dealer (Parts + Labour) | Specialist (Parts + Labour) | What It Involves | Suitability | Estimated Time |
|---|---|---|---|---|---|
 Minor - Swirl flap linkage repair Minor | £300-£600 | £200-£400 | Repair or replace broken swirl flap linkages, clean intake manifold | If caught before actuator fails | 1 - 2 days |
 Intermediate - Swirl flap actuator replacement Best Value | £500-£900 | £350-£650 | Replace swirl flap actuator, inspect vacuum lines, clear fault codes | If actuator has failed | 1 - 2 days |
Full Replacement - Rebuilt OM646 engine Best Value | £4,000-£5,500 | £2,000-£3,200 | Complete engine swap with new intake manifold components, 12-month warranty | If swirl flap failure has caused engine damage | 1 - 2 days |
Vehicle Value Check
Vehicle Value Check
A typical 2004-2010 SLK 200 CDI is worth approximately £3,000-£8,000 depending on condition and mileage. These diesel roadsters offer excellent value for money, making engine replacement a justifiable investment for well-maintained examples.
Our Recommendation
Our Recommendation
Swirl flap issues on the OM646 are common but often repairable. If your SLK 200 CDI experiences rough running or loss of power, have the intake manifold inspected immediately. Specialist swirl flap repair at £200-£400 is significantly cheaper than dealer rates. If the actuator has failed, replacement at £350-£650 is a cost-effective solution. On an SLK 200 CDI worth £3,000-£8,000, this is a worthwhile investment.
Don't Let Swirl Flap Failure, Timing Chain Wear, or DPF Issues Write Off Your Mercedes SLK 200 CDI
Whether you're facing OM646 swirl flap actuator failure on your R171 SLK 200 CDI or OM651 timing chain tensioner issues on your R172, EnginesMarket makes it simple to compare quotes from trusted UK Mercedes diesel specialists. Every rebuilt engine in our network carries upgraded components addressing the original design weakness - reinforced swirl flap linkages, improved timing chain tensioners, and new emission system components - plus a minimum 12-month unlimited mileage warranty with nationwide delivery and supply & fit options. Don't pay main dealer premiums. Compare prices from independent Mercedes diesel specialists who know these 2.1-litre CDI engines inside out.
Compare rebuilt OM646 Mercedes SLK 200 CDI engine prices
12-Month Minimum
UK Specialists Vetted
Best Price GuidanceImportant Information
Important Information
"All prices are indicative UK market ranges based on historical quote data and repair requests from our network of engine specialists. Dealer pricing is estimated based on published main dealer labour rates and genuine OEM parts pricing. Specialist pricing reflects actual quote data from EnginesMarket's UK network. Actual costs vary depending on damage severity, vehicle condition, variant, and workshop location within the UK. Use our free comparison tool to get tailored quotes for your specific Mercedes SLK 200 CDI. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited mileage warranty - always confirm exact terms with your chosen supplier."
Mercedes Benz SLK 200 CDI Engine ReplacementFrequently Asked Questions
Question 1How much does a Mercedes SLK 200 CDI engine replacement cost in the UK-
Short summary: A rebuilt OM646 engine for the R171 SLK 200 CDI costs £2,000-£3,200 supply-only; a rebuilt OM651 engine for the R172 SLK 200 CDI costs £2,200-£3,600 supply-only. Fitting adds £800-£1,500 depending on complexity - diesel work requires specialist knowledge.
- SLK 200 CDI (OM646.980): rebuilt unit £2,000-£3,200; used engine from £900
- SLK 200 CDI (OM651.980): rebuilt unit £2,200-£3,600; used engine from £1,000
- OM646 swirl flap actuator replacement: £350-£650 at specialist
- OM651 timing chain tensioner replacement: £1,400-£2,200 at specialist
Question 2What are the signs of swirl flap failure on a Mercedes SLK 200 CDI-
Short summary: Rough running, loss of power, and check engine lights are the classic warning signs on the OM646 engine. The plastic swirl flap linkages can break, causing the actuator to fail. Vacuum line cracks can also cause similar symptoms.
- Rough idling or hesitation under acceleration
- Loss of power or reduced performance
- Check engine light with intake manifold fault codes
- If caught early, linkage repair costs £200-£400 at specialist
Question 3What are the signs of timing chain failure on a Mercedes SLK 200 CDI (OM651)-
Short summary: A rattling noise on cold start is the classic warning sign on the OM651 engine. The rear-mounted timing chain tensioner can lose pressure, allowing chain slack and guide wear.
- Rattling noise on cold start lasting 1-3 seconds - earliest warning
- Check engine light with timing correlation codes
- Metallic debris in the engine oil (severe cases)
- If caught early, timing chain replacement costs £1,400-£2,200 at specialist
Question 4Is the Mercedes SLK 200 CDI engine reliable-
Short summary: The OM646 and OM651 diesel engines are fundamentally efficient and robust, but both have known weak points. The OM646's swirl flap actuator and DPF issues are common but manageable, while the OM651's timing chain tensioner requires proactive attention.
- OM646 is reliable but swirl flap and DPF issues are common
- OM651 timing chain tensioner wear is the main concern
- Regular oil changes with correct spec oil are essential for both engines
- Regular motorway driving helps prevent DPF regeneration issues
Question 5How long do Mercedes SLK 200 CDI engines last-
Short summary: Properly maintained OM646 and OM651 engines routinely reach 150,000-200,000 miles before major work. Timing chain issues on the OM651 typically appear between 70,000-100,000 miles.
- OM646 (SLK 200 CDI): 150,000-200,000 miles with regular servicing
- OM651 (SLK 200 CDI): 150,000-200,000 miles - timing chain inspection from 70k miles
- DPF regeneration issues can occur on short-journey driving patterns
- Service interval is 10,000 miles or 12 months - use Mercedes-spec low-SAPS oil
Question 6Is it worth replacing the engine in my Mercedes SLK 200 CDI-
Short summary: Yes, if the SLK is otherwise in good condition with no rust or major transmission faults. A rebuilt OM646 costs £2,000-£3,200 - far less than replacing a £3,000-£12,000 vehicle. SLK 200 CDI values remain strong for well-maintained examples, making engine replacement a worthwhile investment.
- SLK 200 CDI values: £3,000-£12,000 depending on generation, condition and mileage
- Rebuilt engine with upgraded components fixes original weak points
- Supply & fit typically £2,800-£5,100 depending on engine code
- New engine includes 12-month unlimited mileage warranty
Why Choose UsCompare Mercedes SLK 200 CDIEngine PricesToday
500+ OM646 and OM651 diesel engines supplied through our network
12-Month Warranty on every rebuilt SLK 200 CDI engine
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supply & fit available for OM646 and OM651
Comparing quotes for your Mercedes SLK 200 CDI is completely free, with no obligation and no pressure. Enter your registration above to get tailored quotes from UK Mercedes diesel specialists who understand the OM646 and OM651 engines inside out. Whether you need a used engine, a reconditioned unit, or a full rebuilt engine with upgraded swirl flap components, timing chain tensioners, and emission system parts, we'll connect you with the right specialist for your exact SLK - with a minimum 12-month warranty on every engine supplied.
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