For an OM642 3.0 V6 diesel engine, start with repair. These engines often survive faults that would scrap a four-cylinder, and a £900–£2,000 OM642 engine repair frequently beats a £4,500–£7,000 replacement Mercedes engine supplied and fitted in the UK.
| Route | Supplied and fitted | Cover | Choose it when |
| Swirl flap and inlet repair | £900–£1,800 | 12 months typical | Flaps, manifold, actuator faults |
| Oil cooler seal replacement | £1,200–£2,200 | 12 months typical | Oil in the coolant, leaks |
| Turbo repair or replacement | £900–£2,400 | 12 months typical | Boost loss, smoke |
| Used OM642 engine fitted | £3,400–£5,200 | 30–90 days | Bottom-end damage |
| Reconditioned OM642 engine fitted | £4,500–£7,000 | 12 months written | Cars you keep long term |
| Model | Years | Code | Note |
| E-Class W211 / W212 | 2005–2016 | OM642 | Swirl flaps, oil cooler seals |
| E-Class W213 | 2016–2018 | OM642 revisions | Improved, same layout |
| S-Class / GLE / ML | 2006–2018 | OM642 | Same family, more weight |
Confirm the code against your REG and the Mercedes parts catalogue before ordering a Mercedes E-Class replacement engine. OM642 power outputs differ, as do the software, turbo and injector specifications.
Three of those five are common OM642 engine repairs, not replacements. That is why an accurate Mercedes diesel engine diagnostic test matters more than the first quote.
A used Mercedes OM642 engine supplied and fitted in the UK typically costs £3,400–£5,200, while a reconditioned Mercedes E-Class OM642 engine supplied and fitted is usually £4,500–£7,000.
Yes. An OM642 swirl flap repair and inlet-manifold repair typically costs £900–£1,800 and usually does not require a replacement engine.
The usual cause is failed OM642 oil cooler seals. It is a known Mercedes 3.0 V6 diesel fault and can normally be repaired without replacing the engine.
A used OM642 engine can be a sensible option for an older E-Class when it comes with a compression test, verified mileage information and a written engine warranty.
Five to ten days for a used engine and two to four weeks for a reconditioned unit.
To verify an OM642 engine code, decode the REG, match it against the Mercedes parts catalogue, then confirm the injector and turbo specifications. Output variants of the Mercedes 3.0 V6 diesel engine differ in software and some hardware.
On most E-Class models, a Mercedes engine fitting specialist removes the engine from above, separates the gearbox and dresses back the front end. A typical OM642 engine replacement takes three to five working days in the workshop.
Keep the first 500 miles gentle and check fluids daily. The 3.0 V6 is a heavy, torquey engine and benefits from a proper running-in period.
Yes, especially on a low-mileage car. An OM642 engine rebuild can be worthwhile when the block and crank are sound. Expect two to four weeks and ask for a documented tolerance report before approving a reconditioned Mercedes engine.
Old parts, printed codes, road test notes and the warranty certificate. On an OM642, also confirm the oil cooler seals and inlet gaskets were replaced.
| Item | Typical cost |
| Swirl flap and inlet repair | £900–£1,800 |
| Oil cooler seal replacement | £1,200–£2,200 |
| Used OM642 engine, supplied and fitted | £3,400–£5,200 |
| Reconditioned unit, supplied and fitted | £4,500–£7,000 |
| Hire car per week | £250–£500 |
| Post-fit oil change | £110–£170 |
Only if you plan to keep the car and the rest of it is sound. On a well-maintained E-Class, a warrantied Mercedes replacement engine can offer better long-term value than changing cars and paying the difference.
The biggest mistake is accepting a Mercedes OM642 engine replacement quote without live data to confirm the diagnosis. Three of the five common OM642 faults can often be repaired without replacing the complete engine.
Ask for the live data: swirl flap position, oil pressure, boost figures and injector leak-off. A specialist who can show you numbers is diagnosing; one who only reads codes is guessing.
The fastest safe route is an OM642 diagnostic check first, because a £1,500 repair can solve what looks like a £6,000 problem. Move to a replacement E-Class engine supplied and fitted only when live data justifies it.
| Scenario | Recommended action | Note |
| Swirl flap fault | Repair | £900–£1,800, no engine needed |
| Oil cooler seals leaking | Repair | Known fault, repairable |
| Turbo actuator failure | Repair | Common and contained |
| Bottom-end knock | Replacement engine | Damage beyond economic repair |
| Head and block damage | Replacement or rebuild | Compare both properly |
Get a Mercedes OM642 specialist diagnosis before you spend: most common faults are repairable, while genuine internal damage may justify a used or reconditioned OM642 engine supplied and fitted in the UK.
Yes, ideally. A Mercedes engine specialist in the UK should have compatible diagnostic equipment for coding, adaptations and injector programming, plus practical experience with OM642 swirl flap and oil cooler seal repairs.
On a 7G-Tronic car over 100,000 miles, a fluid and filter service while the car is in the workshop is worthwhile. On a manual, a clutch at the same time is sensible.
Coolant temperature under load, oil pressure behaviour at idle when hot, and any sign of oil in the coolant expansion tank. Those three checks catch the classic OM642 issues early, when they are still repairs rather than replacements, and they take ten minutes.
On a car with sound heads, injectors and turbo, yes. The 3.0 V6 rebuilds well, and a short engine avoids paying for parts that test within specification. Ask for bore measurements and a head pressure test in writing, and confirm the oil cooler seals are renewed during assembly.
