Mercedes Benz CLS 350/500 Petrol Engine ReplacementCompare Prices & Get Quotes

A Mercedes CLS 350 or CLS 500 replacement engine typically costs between £2,200 for a used M272 unit and £7,500 for a fully rebuilt M278 V8 engine. Specialist fitting adds £800-£1,500.

• Used M272/M276/M278 engines: £2,200-£5,500 depending on mileage and condition
• Reconditioned units: £3,200-£6,500 supply only
• Rebuilt units: £3,800-£7,500 with 12-month warranty
• Specialist fitting adds £800-£1,500; dealer labour is significantly higher
• 12-month warranty included on all rebuilt units through EnginesMarket

The M272 (2004-2010) has the well-documented balance shaft sprocket failure - a serious issue affecting early production units. The M276 (2011-2018) is more reliable but suffers from timing chain tensioner and NOx sensor issues.

• M272 balance shaft failure affects pre-2008 engines - check engine serial number
• Fault codes P0016/P0017 indicate timing correlation issues
• M276 timing chain rattle on cold start can indicate tensioner wear
• NOx sensor replacement is a common maintenance item on M276 engines
• 2008+ M272 and all M276 engines have improved components

The M272 V6 engine has a balance shaft sprocket made from inadequately hardened steel on early production units. As the sprocket teeth wear, the timing chain becomes slack, causing incorrect camshaft timing.

• Affects CLS 350 (2004-2008, M272 engines below serial #468993)
• Symptoms: check engine light with P0016/P0017 codes, rattling on startup
• Repair is engine-out and labour-intensive - £2,500-£3,800 at a specialist
• 2008+ facelift engines have hardened sprockets and are safe

Common culprits include NOx sensor failure (M276 engines), carbon buildup on intake valves due to direct injection, or failing ignition coils.

• NOx sensors can fail without storing permanent codes
• Carbon cleaning may be required every 50,000-80,000 miles on direct-injection M276 engines
• Check VIN online to confirm if your engine is in the affected balance shaft range
• Ignition coil and spark plug condition can also cause power loss

The M278 is a powerful and rewarding engine, but it has serious potential weaknesses. Timing chain tensioner failure and cylinder wall scoring are the main concerns.

• Timing chain rattle on cold start is common - don't ignore it
• Cylinder wall scoring can cause high oil consumption and eventual engine failure
• Have cylinders bore scoped if oil consumption is excessive
• Oil leaks from cam sensor covers are common but not catastrophic
• Regular oil changes every 10,000 miles are critical for longevity

Well-maintained M272 V6 engines regularly exceed 150,000-200,000 miles. M276 engines are newer but expected to achieve similar mileage. M278 V8s can also reach high mileage, but timing chain and cylinder scoring issues can occur earlier.

• M272: 150k-200k+ miles with regular servicing
• M276: 150k+ miles with NOx sensors as the main maintenance item
• M278: 100k-150k+ miles if timing chain and cylinder scoring are addressed
• Regular oil changes every 10,000 miles are critical for longevity

The CLS 350 uses a 3.5-litre V6 (M272 or M276) producing 272-306 hp, while the CLS 500 uses a 4.7-5.0-litre V8 (M113 or M278) producing 306-408+ hp. The CLS 500 offers significantly more performance but higher running costs.

• CLS 350 (M272/M276): 272-306 hp, V6, smoother and more economical
• CLS 500 (M113/M278): 306-408+ hp, V8, more power and torque
• M278 twin-turbo (2011+) delivers 408 hp and 600 Nm torque
• Both are available with 4MATIC all-wheel drive on later models