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Mercedes-Benz OM612 Engine - Replacement Cost, Problems & CompatibilityProblems & Compatibility
The OM612 is Mercedes-Benz’s 2.7-litre inline-5 common-rail diesel (CDI), bridging the gap between the 4-cylinder OM611 and the V6 OM642 in models like the W211 E-Class and W163 M-Class. Reconditioned OM612 engines typically start from £2,800 , serving as a highly sought-after unit for classic and high-mileage Mercedes restorations.
Supply & Fit Available
12-Month Warranty
Nationwide Delivery
100+ Suppliers
Used from
£800
Reconditioned from
£2,800
Rebuilt from
£4,000
GB
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Key Specs
Mercedes-Benz OM612 - Specifications at a Glance
Engine Code
OM612 (including OM612.990)
Fuel
Diesel
Configuration
2.7L inline-5, DOHC, 20-valve, common-rail (CDI)
Power Output(s)
110 kW (150 hp) - 120 kW (163 hp)
Years Produced
2000-2005
UK Models Fitted
4 Mercedes model families - full list in Compatibility below
Replaced
OM605
Replaced By
OM642
Most Common Failure
Swirl flap motor failure and injector seal weeping
Reconditioned Price Range
£2,800-£4,500 supply-only
Vetted UK specialists for OM612 replacements
Minimum 12-month warranty on reconditioned and rebuilt options
Fitted To
Which Mercedes Models Use the OM612-
The OM612 was the definitive 5-cylinder CDI for Mercedes-Benz in the early 2000s, offering a smooth, torque-rich alternative to the 4-cylinder OM611 and a more fuel-efficient option than the V6 OM642.
| Model | Generation/Chassis | Badge(s) | Years | Link |
|---|---|---|---|---|
 Mercedes-Benz C-Class | W203 | C 270 CDI | 2000-2005 | |
| Mercedes-Benz E-Class | W210 | E 270 CDI | 2000-2002 | |
| Mercedes-Benz E-Class | W211 | E 270 CDI | 2002-2005 | |
| Mercedes-Benz M-Class | W163 | ML 270 CDI | 2000-2005 | |
| Mercedes-Benz G-Class | W463 | G 270 CDI | 2001-2005 |
02
Mercedes-Benz E-Class
03
Mercedes-Benz E-Class
04
Mercedes-Benz M-Class
05
Mercedes-Benz G-Class
CROSS-BRAND
OM612 is documented across 5 BMW applications spanning C-Class, E-Class, M-Class, G-Class. Registration lookup confirms the exact suffix before quotes are sent.
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Not sure which engine your car has- Enter your registration above - we'll confirm your exact OM612 fitment before any quotes are sent.
Prices
Mercedes-Benz OM612 Engine Replacement Cost (UK)
Condition | Supply Only | Fitted (Independent Specialist) | Typical Warranty |
|---|---|---|---|
Used | £800-£1,500 | £1,400-£2,500 | 3-6 months |
Reconditioned | £2,800-£4,500 | £3,500-£5,500 | 12-24 months |
Rebuilt | £4,000-£6,000 | £4,800-£7,200 | 12-24 months |
What genuinely moves the price for this engine is the condition of the swirl flap system, injector seals, and turbocharger actuator. Because the OM612 is an early common-rail design, recon specialists often upgrade the swirl flap mechanism to a more reliable aftermarket unit or perform a verified delete, alongside replacing all injector seals as standard. For a full breakdown of market rates, see our full reconditioned engine cost guide.
Labour Guide
Fitting an OM612 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 OM612 Engine Problems - What Actually Fails
Every engine has its weak points. Here are the known issues with the OM612, based on real-world data and verified failure patterns.
Verified issue focus: Swirl flap motor failure and injector seal weeping.
1. Swirl Flap Motor Failure - All variants
1. Swirl Flap Motor Failure - All variants
Typical onset:
80,000-120,000 miles
What happens:
The plastic gears inside the electronic swirl flap motor strip over time, causing the ECU to throw a check engine light and default the engine to limp mode. In some cases, the flaps themselves can seize in the inlet manifold due to carbon 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
2. Injector Seal Weeping ("Black Death") - All variants
2. Injector Seal Weeping ("Black Death") - All variants
Typical onset:
100,000+ miles
What happens:
The copper washer seals at the base of the injectors degrade, allowing high-pressure combustion gases to escape. This creates a black, crusty carbon buildup around the injector heads, leading to a distinct tapping noise, rough idling, and a strong smell of exhaust in the cabin.
Repair vs replace:
This is a routine maintenance item, not a terminal failure. Replacing the seals and cleaning the cylinder head is inexpensive and should be done preventatively.
Read more about this issue
3. Turbocharger Actuator Wear - High-mileage units
3. Turbocharger Actuator Wear - High-mileage units
Typical onset:
100,000+ miles
What happens:
The wastegate actuator rod and linkage can corrode or seize, leading to inconsistent boost pressure, sluggish acceleration, and potential over-boosting if the flap sticks closed.
Repair vs replace:
Actuator replacement is a straightforward and cost-effective repair. If the turbocharger internals have suffered damage from prolonged over-boosting, a full turbo rebuild or replacement is necessary.
Read more about this issue
The OM612 is generally more robust than the 4-cylinder OM611 it succeeded, featuring a stronger block and fewer timing chain issues. Units maintained with regular oil changes and timely injector seal replacements routinely exceed 250,000 miles without major internal issues .
Compare rebuilt OM612 engine prices with the failure already addressed
Engine Variants
How to Confirm You Have the Mercedes-Benz OM612
The engine code is stamped on the right-hand side of the cylinder block, just above the oil filter housing. It will also be listed on your V5C logbook under "Engine Capacity" or visible via a VIN decode. The OM612 is sometimes confused with the 4-cylinder OM611 or the V6 OM642. Fitting the wrong revision or assuming interchangeability matters significantly: the OM612 has a unique 5-cylinder firing order, specific engine mounts, and a distinct wiring loom and ECU mapping that will not function correctly in a 4- or 6-cylinder chassis.
Not sure which engine your car has- Enter your registration above - we'll confirm your exact OM612 fitment before any quotes are sent.
Easily Confused
OM605
the 2.5L inline-5 pre-chamber diesel that the OM612 replaced, sharing the same smooth 5-cylinder firing order but lacking the efficiency and torque of the common-rail architecture.
Alternative / Next-Gen Code
OM642
the 3.0L V6 CDI that largely took over the mid-range torque role in later E-Class and M-Class models, offering higher outputs but with a more complex V-layout and different failure profile.
Related JLR Variants
OM611
the smaller 2.1L/2.2L 4-cylinder CDI that sits directly below the OM612 in the hierarchy, sharing the same electronic injection principles but with less low-end pulling power.
Confirm the exact OM612 fitment
Not sure which engine your car has- Enter your registration above - we'll confirm your exact OM612 fitment before any quotes are sent.
Buying Guide
Buying a Replacement OM612 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 OM612 engine makes sense only if it comes with verifiable service history and documented replacement of the swirl flap actuator and injector seals. Given the age of these vehicles, the primary risk is hidden carbon buildup or degraded rubber components, so a compression test is mandatory before purchase.
Reconditioned:
A proper reconditioned OM612 engine is the sweet spot for most buyers. A reputable rebuild will address the common failure points by upgrading or replacing the swirl flap system, fitting new injector seals, and refreshing the turbo actuator, giving the engine a fresh lease on life.
Rebuilt:
A full OM612 engine rebuild is justified for high-mileage G-Class applications or classic W211 E-Class restorations 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 OM612 engine is installed by specialists familiar with early Mercedes CDI systems, backed by a nationwide warranty.
Vehicle Value Note:
Because the OM612 is typically found in W203, W210, W211, W163, and W463 vehicles valued between £2,000 and £8,000, 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 .
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Related Engines
Engines Related to the Mercedes-Benz OM612
Explore engines that are closely related to the Mercedes-Benz OM612, including its predecessor, successor, and key family variants.
Predecessor
OM605
the 2.5L inline-5 pre-chamber diesel that the OM612 replaced, sharing the same smooth 5-cylinder firing order but lacking the efficiency and torque of the common-rail architecture.
Successor
OM642
the 3.0L V6 CDI that largely took over the mid-range torque role in later E-Class and M-Class models, offering higher outputs but with a more complex V-layout and different failure profile.
Sibling
OM611
the smaller 2.1L/2.2L 4-cylinder CDI that sits directly below the OM612 in the hierarchy, sharing the same electronic injection principles but with less low-end pulling power.
Sibling
OM646
the later 2.1L/2.2L 4-cylinder CDI that replaced the OM611, often confused with the OM612 due to overlapping production years in the W211 E-Class, though it is physically a different block.
FAQ
Mercedes-Benz OM612Frequently Asked Questions
Question 1How much does a Mercedes OM612 engine replacement cost-
A reconditioned Mercedes OM612 engine typically costs between £2,800 and £4,500 for supply only . Fitted costs generally range from £3,500 to £5,500 depending on the specialist, while used units can be found from £800 but carry higher risk due to the engine's age. Compare OM612 engine replacement quotes today
Compare OM612 quotesQuestion 2What is the most common failure on the OM612 engine-
The most documented issues are swirl flap motor failure, injector seal weeping ("Black Death"), and turbocharger actuator wear. Swirl flap motor failure triggers limp mode and is a routine fix, whereas injector seal failure causes black carbon buildup and rough idling but is a cheap and preventative maintenance item. Get quotes for a rebuilt OM612 with these issues resolved
Compare OM612 quotesQuestion 3Which Mercedes models use the OM612 engine-
The OM612 was fitted to the W203 C-Class (C 270 CDI), the W210 and W211 E-Class (E 270 CDI), the W163 M-Class (ML 270 CDI), and the W463 G-Class (G 270 CDI), serving as the definitive 5-cylinder diesel for these chassis between 2000 and 2005. Check your registration to confirm your exact OM612 fitment
Compare OM612 quotesQuestion 4Should I buy a used or reconditioned OM612 engine-
A reconditioned OM612 is strongly recommended over a used unit. A proper rebuild will proactively address the common failure points by upgrading or replacing the swirl flap system, fitting new injector seals, and refreshing the turbo actuator, whereas used engines often hide stretched components and carboned manifolds. Compare reconditioned OM612 engine prices from UK specialists
Compare OM612 quotesQuestion 5How do I know if my car has the OM612 and not the OM611 or OM642-
The OM612 is a distinct 2.7L inline-5, producing a unique 5-cylinder rumble compared to the 4-cylinder OM611 or the V6 OM642. The engine code is stamped on the right-hand side of the cylinder block above the oil filter housing and is also listed on your V5C logbook. Enter your reg above to identify your exact engine code ═══════════════════════════════════════
Compare OM612 quotesCompare Mercedes-Benz OM612 Engine Prices Today
Vetted UK specialists who work on classic Mercedes CDI systems like the OM612 every week Minimum 12-month warranty on every reconditioned and rebuilt OM612 engine Nationwide delivery - supply-only or full supply & fit available across the UK Get a free, no-obligation comparison of OM612 engine prices tailored to your exact vehicle. Our registration lookup confirms your fitment before any quotes are sent, ensuring you receive the correct unit with matching ancillary components. With reconditioned OM612 engines starting from an estimated £2,800, comparing takes two minutes and could save you hundreds on labour and unexpected parts.
Vetted UK Specialists
Vetted UK specialists for OM612 replacements
Minimum 12-Month Warranty
Minimum 12-month warranty on reconditioned and rebuilt options
Nationwide Delivery
Nationwide delivery plus supply and fit availability
Expert Support
Secure enquiry - no spam. Quotes only from vetted UK engine specialists.
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