Mercedes Benz CLS 220/250 CDI Engine ReplacementCompare Prices & Get Quotes

A Mercedes CLS 220 BlueTEC or CLS 250 CDI replacement engine typically costs between £1,800 for a used unit and £4,500 for a fully rebuilt OM651 engine. Specialist fitting adds £400-£800.

• Used OM651 engines: £1,800-£3,000 depending on mileage and condition
• Reconditioned units: £2,800-£4,000 supply only
• Rebuilt units: £3,200-£4,500 with 12-month warranty
• Specialist fitting adds £400-£800; dealer labour is significantly higher
• 12-month warranty included on all rebuilt units through EnginesMarket

Yes - the OM651 is fundamentally a reliable engine, with many examples exceeding 200,000-300,000 km. However, it has predictable weak points: timing chain stretch and guide wear from approximately 120,000 km, EGR valve clogging, swirl flap failure, and injector seal leaks ("Black Death").

• OM651 is robust and capable of high mileage with proper maintenance
• Timing chain rattle on cold start is the early warning sign
• Regular oil and filter changes every 10,000 miles are critical for longevity
• A 2015 recall addressed timing chain tensioner seal ring oil leaks

"Black Death" is the common term for injector seal failure on Mercedes diesel engines. When the seals fail, unburnt diesel and exhaust gases escape, creating a hard, tar-like carbon buildup around the injector seats.

• Symptoms: chuffing noise from engine bay, black residue around injectors, fuel odour
• If ignored, injectors can seize and cylinder head damage can occur
• Specialist seal replacement costs £300-£500
• Catch it early - the repair is far cheaper than engine replacement

Well-maintained OM651 engines regularly exceed 150,000-200,000 miles. With meticulous maintenance, some have reached 300,000 miles without major failures.

• OM651: 150k-200k+ miles with regular servicing
• Timing chain stretch typically occurs from 75,000-120,000 miles
• Regular oil changes every 10,000 miles significantly extends life

Timing chain replacement on a CLS 220/250 CDI OM651 engine costs £1,200-£1,800 at a specialist or £1,800-£2,800 at a main dealer. This is preventative work. If the chain has already slipped, full engine replacement at £3,200-£4,500 is required.

• Specialist preventative chain replacement: £1,200-£1,800
• Dealer pricing for same work: £1,800-£2,800
• The chain is on the transmission side, making access restricted and replacement expensive
• Rattling noise on cold start is the early warning sign

On a CLS 220/250 CDI worth £5,000-£10,000, specialist engine replacement at £3,200-£4,500 is worthwhile if the body and interior are in excellent condition. However, if the car has rust, electrical issues, or poor bodywork, consider scrapping it.

• A clean, well-maintained CLS is worth saving
• Rebuilt OM651 with upgraded timing components and seals costs £3,200-£4,500 supply only
• If the car has other major issues, replacement may not be cost-effective

Both use the same OM651.924 engine family. The CLS 220 BlueTEC is a lower-power version (168-170 hp) while the CLS 250 CDI produces 204 hp. The difference is primarily in engine mapping and turbocharger specification, not mechanical hardware.

• Same engine block, cylinder head and bottom end
• Power difference is electronic mapping and turbo spec
• Reliability is identical between the two variants
• Replacement engines are interchangeable with correct ECU programming