Mercedes Benz CLS 63 AMG Engine ReplacementCompare Prices & Get Quotes

A Mercedes CLS 63 AMG replacement engine typically costs between £3,500 for a used M156 unit and £12,000 for a fully rebuilt M157 engine. Specialist fitting adds £800-£1,500.

• Used M156/M157 engines: £3,500-£6,500 depending on mileage and condition
• Reconditioned units: £5,000-£8,000 supply only
• Rebuilt units: £6,500-£12,000 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 M156 is a masterpiece of engineering, but early engines have a critical weakness: cylinder head bolt failure. Camshaft adjuster wear is also common.

• Head bolt failure affects pre-2011 M156 engines - check engine serial number
• Symptoms: coolant loss, white smoke, misfire on cold start
• Preventative head bolt upgrade costs £2,800-£4,000 at an AMG specialist
• Camshaft adjuster rattle on startup indicates wear
• With head bolts addressed, the M156 is a robust and rewarding engine

The M156 engine uses torque-to-yield cylinder head bolts that can stretch and snap under extreme heat and pressure. When a bolt fails, coolant can leak into the combustion chamber.

• Affects pre-2011 M156 engines up to serial number 60658
• Symptoms: unexplained coolant loss, misfire on cold start, white smoke
• If ignored, hydro-lock can bend connecting rods and write off the engine
• Preventative head bolt upgrade with ARP or Weistec studs is strongly recommended
• Specialist preventative work costs £2,800-£4,000

The M157 twin-turbo V8 is generally more reliable than the M156, but it has known weaknesses: timing chain tensioner failure and high-pressure fuel pump failure.

• Timing chain rattle on cold start is common - don't ignore it
• Install non-return valves and updated tensioners as preventative maintenance
• HPFP failure causes misfires and power loss under load
• Cylinder wall scoring can occur in some units
• Regular oil changes every 10,000 miles are critical for longevity

Timing chain replacement on a CLS 63 AMG M157 engine costs £2,500-£3,800 at a specialist or £3,500-£5,000 at a main dealer. This is preventative work. If the chain has already slipped, full engine replacement at £6,000-£7,500 is required.

• Specialist preventative chain replacement: £2,500-£3,800
• Dealer pricing for same work: £3,500-£5,000
• Rattling noise on cold start is the early warning sign
• Once timing jumps, valves contact pistons - engine is beyond repair

On a CLS 63 AMG worth £12,000-£40,000, specialist engine replacement at £6,500-£12,000 is worthwhile if the body and interior are in excellent condition. CLS 63 AMG values are stable and, in some cases, rising - they are modern classics.

• A clean, well-maintained CLS 63 AMG is worth saving
• Rebuilt M156/M157 engines cost £6,500-£12,000 supply only
• Compare against £10,000-£15,000 main dealer new engine quotes
• If the car has rust, electrical issues, or poor bodywork, consider scrapping it

The M157 is generally considered more reliable than the M156, but both have their weaknesses. The M156 has the well-documented head bolt failure, while the M157 suffers from timing chain tensioner and HPFP issues.

• M156 (2006-2011): legendary naturally aspirated V8, but head bolt failure is a critical concern
• M157 (2011-2017): more power and torque, twin-turbo, generally more reliable but has timing chain and fuel system weaknesses
• The M156 is more rewarding to drive and listen to; the M157 is faster and more refined
• Both engines are expensive to maintain and repair - budget accordingly