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Mercedes-Benz OM642 Engine - Replacement Cost, Problems & CompatibilityProblems & Compatibility
The OM642 is Mercedes-Benz’s 3.0-litre V6 common-rail diesel (CDI), fitted to the W211/W212 E-Class, W164 M-Class, W166 GLE, and W221 S-Class. Reconditioned OM642 engines typically start from £3,200 , and with 880 UK replacement requests in 2025 , it remains one of the most sought-after units for premium Mercedes restorations and high-mileage repairs.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
Used from
£1,800
Reconditioned from
£3,200
Rebuilt from
£4,500
GB
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Quotes only from vetted UK engine specialists.
Key Specs
Mercedes-Benz OM642 - Specifications at a Glance
Engine Code
OM642 (including OM642.940, OM642.950, OM642.960)
Fuel
Diesel
Configuration
3.0L V6, DOHC, 24-valve, common-rail (CDI)
Power Output(s)
140 kW (190 hp) - 190 kW (258 hp)
Years Produced
2005-2018
UK Models Fitted
5 Mercedes model families - full list in Compatibility below
2025 UK Replacement Requests
880
Replaced
OM648 / OM613
Replaced By
OM656
Most Common Failure
Oil cooler seal leak (V-valley O-ring) and swirl flap motor failure
Reconditioned Price Range
£3,200-£5,500 supply-only
Vetted UK specialists for OM642 replacements
Minimum 12-month warranty on reconditioned and rebuilt options
Fitted To
Which Mercedes Models Use the OM642-
The OM642 was the definitive V6 diesel for Mercedes-Benz throughout the late 2000s and 2010s, bridging the gap between the 4-cylinder OM651 and the V8 OM628/OM629, offering a smooth balance of torque, refinement, and efficiency.
| Model | Generation/Chassis | Badge(s) | Years | Link |
|---|---|---|---|---|
 Mercedes-Benz E-Class | W211 | E 280 CDI, E 320 CDI | 2005-2009 | |
| Mercedes-Benz E-Class | W212 | E 300 CDI, E 350 CDI | 2009-2016 | |
| Mercedes-Benz S-Class | W221 / W222 | S 320 CDI, S 350 CDI, S 400 CDI | 2006-2017 | |
| Mercedes-Benz CLS-Class | C218 / C219 | CLS 350 CDI | 2006-2018 | |
| Mercedes-Benz GLK-Class | X204 | GLK 220 CDI, GLK 250 CDI, GLK 350 CDI | 2008-2015 | |
| Mercedes-Benz M-Class | W164 | ML 280 CDI, ML 320 CDI, ML 350 CDI | 2005-2011 | |
| Mercedes-Benz GLE-Class | W166 | GLE 350 d | 2015-2018 |
02
Mercedes-Benz E-Class
03
Mercedes-Benz S-Class
04
Mercedes-Benz CLS-Class
05
Mercedes-Benz GLK-Class
06
Mercedes-Benz M-Class
Generation/Chassis
W164
Badge(s)
ML 280 CDI, ML 320 CDI, ML 350 CDI
Years
2005-2011
07
Mercedes-Benz GLE-Class
CROSS-BRAND
OM642 is documented across 7 BMW applications spanning E-Class, S-Class, CLS-Class, GLK-Class, M-Class, GLE-Class. Registration lookup confirms the exact suffix before quotes are sent.
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Prices
Mercedes-Benz OM642 Engine Replacement Cost (UK)
Condition | Supply Only | Fitted (Independent Specialist) | Typical Warranty |
|---|---|---|---|
Used | £1,800-£3,200 | £2,450-£4,110 | 3-6 months |
Reconditioned | £3,200-£5,500 | £3,850-£6,410 | 12-24 months |
Rebuilt | £4,500-£7,000 | £5,150-£7,910 | 12-24 months |
What genuinely moves the price for this engine is whether the notorious V-valley oil cooler O-ring and swirl flap motor have been proactively replaced, and the condition of the turbocharger seals. Because the OM642 is a complex V6 layout, recon specialists will typically strip the intake manifold to clean carbon buildup and replace all critical seals as standard. For a full breakdown of market rates, see our full reconditioned engine cost guide.
Labour Guide
Fitting an OM642 engine typically takes 10-14 hours at £65-£85/hr (independent) - confirm exact labour when comparing quotes.
Price Factors
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Common Problems
Mercedes-Benz OM642 Engine Problems - What Actually Fails
Every engine has its weak points. Here are the known issues with the OM642, based on real-world data and verified failure patterns.
Verified issue focus: Oil cooler seal leak (V-valley O-ring) and swirl flap motor failure.
1. Oil Cooler Seal Leak (V-Valley O-Ring) - All variants
1. Oil Cooler Seal Leak (V-Valley O-Ring) - All variants
Typical onset:
70,000-150,000 miles
What happens:
The rubber O-ring sealing the oil cooler, located deep in the V of the engine, degrades over time. This allows oil to leak downwards, pooling on the hot exhaust manifold (creating smoke and a potential fire risk) or dripping onto the driveway.
Repair vs replace:
The O-ring itself costs under £20, but the labour is intensive (10+ hours) due to the need to remove the intake manifold and associated components. If neglected, it rarely causes catastrophic internal engine damage, but a full replacement is only required if severe overheating or fire damage has occurred.
Read more about this issue
2. Swirl Flap Motor Failure - All variants
2. Swirl Flap Motor Failure - All variants
Typical onset:
70,000-150,000 miles
What happens:
The plastic gears inside the electronic swirl flap actuator motor strip over time. This causes the ECU to throw a check engine light and default the engine to limp mode, severely restricting power. In some cases, the flaps themselves can seize in the inlet manifold due to heavy EGR soot buildup.
Repair vs replace:
The actuator motor can be replaced independently and relatively cheaply. However, if the flaps are seized or the manifold is heavily carboned, a full inlet manifold replacement or verified delete is required.
Read more about this issue
3. Turbocharger Seal Leaks - High-mileage units
3. Turbocharger Seal Leaks - High-mileage units
Typical onset:
100,000+ miles
What happens:
The wastegate actuator or internal turbo seals can degrade, leading to oil consumption, blue smoke from the exhaust, and a noticeable loss of boost pressure.
Repair vs replace:
Actuator replacement or a turbo rebuild is a straightforward and cost-effective repair. If the turbocharger internals have failed and sent metal debris through the intercooler and into the engine, a full engine replacement is necessary.
Read more about this issue
The OM642 is generally considered a robust and durable V6 diesel. Units maintained with strict oil change intervals and timely preventative replacement of the oil cooler O-ring routinely exceed 200,000 miles without major internal issues .
Compare rebuilt OM642 engine prices with the failure already addressed
Engine Variants
OM642 Sub-Codes Explained - Which One Is in Your Car-
INTRO: The OM642 family shares the same fundamental 3.0L V6 block and common-rail architecture, but displacement tuning, turbocharging, and calibration vary depending on the chassis. Identifying your exact sub-code ensures you order the correct injection pump, turbo, and ancillary components. - Fitted to: E-Class W211 (E 280 CDI, E 320 CDI), M-Class W164 - Key technical difference: The earlier variant of the OM642 family, typically paired with the 7G-Tronic transmission and featuring a slightly lower output tune. - Sub-code-specific failure note: Shares the family failure pattern above; early builds are particularly prone to the V-valley oil cooler O-ring leak. - Interchange note: Not a straight swap with the .960 high-output variants; the ECU mapping, turbo plumbing, and injection pump calibration differ significantly. - Fitted to: E-Class W212 (E 300 CDI, E 350 CDI), CLS-Class C218, GLK-Class X204 - Key technical difference: A higher-output tune featuring revised piezo-electric injectors in later builds, designed to deliver stronger mid-range torque for heavier saloon and SUV chassis. - Sub-code-specific failure note: Shares the family failure pattern above; swirl flap motor failure is highly prevalent on this specific tune due to higher EGR flow. - Interchange note: Requires matching ECU and turbo setup; the sump, oil pickup, and engine mounts differ between the W212 and X204 applications. - Fitted to: S-Class W221 / W222 (S 400 CDI), GLE-Class W166 - Key technical difference: The highest output variant, featuring a twin-scroll turbocharger, upgraded cooling systems, and reinforced internal components to handle the increased thermal and mechanical loads of flagship vehicles. - Sub-code-specific failure note: Shares the family failure pattern above; turbocharger seal wear is slightly more prevalent due to the higher boost pressures. - Interchange note: Cannot be swapped with the .940 or .950 without significant ECU, wiring loom, and hardware changes.
The engine code is stamped on the left-hand side of the cylinder block, near the bellhousing. It will also be listed on your V5C logbook under "Engine Capacity" or visible via a VIN decode. Not sure- Enter your registration above for instant confirmation.
Easily Confused
OM613
the 3.2L inline-5 CDI that the OM642 effectively replaced in the upper-midrange and flagship diesel slot, offering a shift to a smoother, more powerful V6 architecture.
Alternative / Next-Gen Code
OM656
the modern 3.0L inline-6 CDI successor that eventually took over the flagship diesel role, delivering comparable torque with improved emissions compliance and a return to the inline configuration.
Related JLR Variants
OM651
the 2.1L/2.2L inline-4 CDI that sits directly below the OM642 in the hierarchy, sharing the same common-rail philosophy but with less displacement and lower output for compact and mid-size chassis.
Confirm the exact OM642 fitment
The engine code is stamped on the left-hand side of the cylinder block, near the bellhousing. It will also be listed on your V5C logbook under "Engine Capacity" or visible via a VIN decode. Not sure- Enter your registration above for instant confirmation.
Buying Guide
Buying a Replacement OM642 Engine - What to Choose
Choosing the right replacement route depends on your budget, risk tolerance, and ownership goals. Here's a breakdown of your options.
Used:
A used OM642 engine makes sense only if it comes with verifiable service history and documented replacement of the V-valley oil cooler O-ring and swirl flap motor. Given the labour-intensive nature of accessing these components, buying a used unit with unknown history often leads to an immediate £1,000+ teardown bill.
Reconditioned:
A proper reconditioned OM642 engine is the sweet spot for most buyers. A reputable rebuild will proactively address the common failure points by replacing the oil cooler O-ring, fitting a new swirl flap motor, and refreshing the turbo seals, giving the engine a fresh lease on life.
Rebuilt:
A full OM642 engine rebuild is justified for high-mileage S-Class or GLE hosts where originality and maximum longevity are required. An upgraded rebuild should include line-boring the block, new pistons/rings, and a balanced crankshaft.
Supply & Fit Line:
Sourcing and fitting through our vetted network ensures your OM642 engine is installed by specialists familiar with Mercedes V6 CDI systems, backed by a nationwide warranty.
Vehicle Value Note:
Because the OM642 is typically found in W212, W221, W166, and X204 vehicles valued between £4,000 and £18,000, a full replacement can represent a significant portion of the host's worth. If the lowest viable replacement cost exceeds approximately 60% of the vehicle's current market value, evaluate scrap value before committing .
Compare OM642 Engine Prices Now
Related Engines
Engines Related to the Mercedes-Benz OM642
Explore engines that are closely related to the Mercedes-Benz OM642, including its predecessor, successor, and key family variants.
Predecessor
OM613
the 3.2L inline-5 CDI that the OM642 effectively replaced in the upper-midrange and flagship diesel slot, offering a shift to a smoother, more powerful V6 architecture.
Successor
OM656
the modern 3.0L inline-6 CDI successor that eventually took over the flagship diesel role, delivering comparable torque with improved emissions compliance and a return to the inline configuration.
Sibling
OM651
the 2.1L/2.2L inline-4 CDI that sits directly below the OM642 in the hierarchy, sharing the same common-rail philosophy but with less displacement and lower output for compact and mid-size chassis.
Sibling
OM646
the later 2.1L/2.2L inline-4 CDI that replaced the OM651, often found alongside the OM642 in the W212 E-Class range, though it is physically a different, smaller block.
FAQ
Mercedes-Benz OM642Frequently Asked Questions
Question 1How much does a Mercedes OM642 engine replacement cost-
A reconditioned Mercedes OM642 engine typically costs between £3,200 and £5,500 for supply only . Fitted costs generally range from £3,850 to £6,410 depending on the specialist, while used units can be found from £1,800 but carry higher risk due to the engine's complexity. Compare OM642 engine replacement quotes today
Compare OM642 quotesQuestion 2What is the most common failure on the OM642 engine-
The most documented issues are the V-valley oil cooler seal (O-ring) leak and swirl flap motor failure. The oil cooler O-ring degrades and leaks oil onto the hot exhaust manifold, while the swirl flap motor gears strip over time, triggering limp mode. Both are routine fixes if caught early but labour-intensive due to engine access. Get quotes for a rebuilt OM642 with these issues resolved
Compare OM642 quotesQuestion 3Which Mercedes models use the OM642 engine-
The OM642 was fitted to the W211 and W212 E-Class (E 280/320/350 CDI), the W221 and W222 S-Class (S 320/350/400 CDI), the C218/C219 CLS-Class, the X204 GLK-Class, the W164 M-Class, and the W166 GLE-Class, serving as the definitive V6 diesel for these chassis between 2005 and 2018. Check your registration to confirm your exact OM642 fitment
Compare OM642 quotesQuestion 4Should I buy a used or reconditioned OM642 engine-
A reconditioned OM642 is strongly recommended over a used unit. A proper rebuild will proactively address the common failure points by replacing the V-valley oil cooler O-ring, fitting a new swirl flap motor, and refreshing the turbo seals, whereas a used engine with unknown history often leads to an immediate £1,000+ teardown bill for these specific repairs. Compare reconditioned OM642 engine prices from UK specialists
Compare OM642 quotesQuestion 5What is the difference between OM642.940, .950, and .960-
The OM642.940 is the earlier, lower-output variant (found in W211 E-Class), the OM642.950 is the mid-output tune (common in W212 E-Class and GLK-Class), and the OM642.960 is the highest-output variant (fitted to S-Class and GLE-Class). They share the same core block, but the injection pumps, turbo plumbing, and ECU mapping differ significantly and are not directly interchangeable. Enter your reg above to identify your exact OM642 sub-code ═══════════════════════════════════════
Compare OM642 quotesCompare Mercedes-Benz OM642 Engine Prices Today
Vetted UK specialists who work on complex Mercedes V6 CDI systems like the OM642 every week Minimum 12-month warranty on every reconditioned and rebuilt OM642 engine Nationwide delivery - supply-only or full supply & fit available across the UK Get a free, no-obligation comparison of OM642 engine prices tailored to your exact sub-code. Our registration lookup confirms your fitment before any quotes are sent, ensuring you receive the correct unit with matching ancillary components. With reconditioned OM642 engines starting from £3,200, comparing takes two minutes and could save you hundreds on labour and unexpected teardowns.
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Minimum 12-Month Warranty
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