Is the Mercedes-AMG CLS63 engine reliable?

It depends entirely on which generation. The M156 (C219) has well-documented head bolt and camshaft issues. The M157 (C218) is considered more reliable when maintained properly, but early examples suffer from timing chain stretch and cylinder scoring. Both demand diligent maintenance with 5,000–10,000 mile oil changes.

What are the common problems with the Mercedes-AMG CLS63?

M156: head bolt corrosion (pre-2011 — the most critical concern), camshaft and lifter wear, cam adjuster rattle, oil leaks. M157: timing chain stretch (2011–2012), cylinder scoring (cylinders 1 and 5), oil wicking into the engine harness, turbo coolant pipe leaks, camshaft sensor oil leaks.

Is it worth replacing a Mercedes-AMG CLS63 engine, or should I scrap the car?

CLS63 values remain strong — a well-kept C218 is often worth £15,000–£35,000+. A £4,500–£11,000 reconditioned engine is 15–40% of the vehicle's value — apply the Mercedes 70% scrap threshold. If the car is a cherished example, replacement is often worthwhile. However, given the costs involved, ensure you understand the full picture before committing.

How do I find my Mercedes-AMG CLS63 engine code?

Listed on the VIN plate and vehicle documentation. C219 CLS63 (2006–2011) uses M156.983; C218 CLS63 (2011–2017) uses M157.981. Tell us your registration date and we'll confirm it for free.

Can I repair the M156 head bolts, or does the engine need replacement?

The head bolts can be replaced — they are a known weak point. Replacement costs £1,600–£5,000. If the bolts fail and cause head gasket problems, the engine can be destroyed. A preventative head bolt replacement is far cheaper than a full engine replacement (£4,500+). At the first sign of clicking on cold start or coolant loss on a pre-2011 M156, book an inspection immediately.

Mercedes-AMG CLS632006–20172 Engine Generations

Mercedes-AMG CLS63 Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes-AMG CLS63 UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

The CLS63 AMG has worn two legendary powertrains — the naturally aspirated 6.2-litre M156 in the first generation and the twin-turbo 5.5-litre M157 in the second. Both deliver breathtaking performance, but timing chain issues, cylinder scoring and oil leaks are well-documented. Get quotes from UK specialists for reconditioned, rebuilt and used units today.

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Mercedes-AMG CLS63 Engines — from £3,000 to £11,759Common codes: M156, M157

Mercedes-AMG CLS63 Engines — from £3,000 to £11,759· Common codes: M156, M157

Instant QuotesNo Obligation100% FreeReconditionedRebuiltUsedSupply & Fit AvailableUK-Wide Network

The CLS63 THROUGH TIME — Era Map

Four generations. Four eras. One guide to reliability, costs and what really matters.

GenerationYearsEngine CodeReliabilityRecon CostEra Note

Why use this era map?

Every cost guide, reliability rating and engine code on this page is aligned to the data above. This keeps everything consistent and trustworthy.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

Mercedes-AMG CLS63 Engine Replacement Costs

Supply Only£4,500–£8,000

Fitted (Indie)£6,500–£10,000

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£3,000–£5,500£5,000–£7,5001–6 monthsBudget priority; older M156 examples

Reconditioned Engine£4,500–£8,000£6,500–£10,00012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£6,500–£11,759£8,500–£14,00012–24 monthsLong‑term ownership; 3+ year horizon

Main Dealer New£12,000–£18,000+£14,000–£21,000+24–36 monthsInsurance jobs, warranty claims

Figures above reflect the current CLS63 AMG market. A replacement M157 engine costs on average £10,888 in good condition, with new or reconditioned units reaching £11,759. Rebuilt M157 engines start from £6,995. Used M156 engines are available from around £3,500–£5,000. See the Era Map above for generation-specific context.

Labour estimate: Fitting a CLS63 AMG engine typically takes 14–20 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer). The V8's complexity and tight engine bay make it a specialist job.

→ Compare CLS63 AMG engine prices from UK specialists

Common Problems

1. M156 Head Bolt Corrosion (C219 — Pre-2011)

Symptoms: Clicking noises on cold start, rising oil level, coolant loss requiring frequent top-ups, head gasket failure, eventual engine failure

Typical mileage: 40,000–80,000 miles

Repair cost: £1,600–£5,000 (head bolt and head gasket replacement)

Replacement cost: £4,500–£8,000 (if head bolt failure destroys the engine)

🔴 Immediate - this is the single biggest risk on the early M156

Our recommendation:

The M156's head bolts corrode due to a design flaw. This issue affected early CLS63 units before AMG updated the bolts in mid-2010. A class action lawsuit was filed alleging Mercedes knew about the problem. If you're buying a pre-2011 CLS63, budget for head bolt replacement immediately. Some owners report head bolt replacement costs around £1,600. A preventative head bolt replacement is far cheaper than a full engine replacement.

Read the full head bolt failure guide

1. M156 Head Bolt Corrosion (C219 — Pre-2011)

Symptoms: Clicking noises on cold start, rising oil level, coolant loss requiring frequent top-ups, head gasket failure, eventual engine failure

Typical mileage: 40,000–80,000 miles

Repair cost: £1,600–£5,000 (head bolt and head gasket replacement)

Replacement cost: £4,500–£8,000 (if head bolt failure destroys the engine)

🔴 Immediate - this is the single biggest risk on the early M156

Our recommendation:

Read the full head bolt failure guide

2. M156 Camshaft and Lifter Wear (C219)

Symptoms: Ticking or tapping noise from the top of the engine on cold start, metallic rattle at start-up, reduced performance, metallic debris in oil

Typical mileage: 50,000–100,000 miles

Repair cost: £2,000–£4,500 (camshaft and lifter replacement)

Replacement cost: £4,500–£8,000 (if wear causes catastrophic engine damage)

🔴 Immediate - if you hear ticking from the top of the engine, have it inspected immediately

Our recommendation:

The M156 suffers from premature camshaft and lifter wear. The camshaft adjusters' locking pins can wear, causing rattle at start-up. If you notice ticking on cold start, have the camshafts and lifters inspected immediately. Regular oil changes with the correct MB-spec oil are essential.

Read the full camshaft and lifter wear guide

3. M157 Timing Chain Stretch (C218 — 2011–2012)

Symptoms: Rattling noise from the front of the engine, engine warning light, cam timing errors, eventual chain slip

Typical mileage: 60,000–100,000 miles

Repair cost: £2,500–£5,000 (timing chain, tensioner and guide replacement)

Replacement cost: £5,500–£9,000 (if chain jumps and causes valve interference)

🔴 Immediate - if the timing chain fails on the M157, the engine is typically destroyed

Our recommendation:

Early M157 engines (2011–2012) have timing chain stretch issues. The problem stems from oil drainage from the cylinder head on initial start-up. Updated non-return valves and revised chain tensioners are available. If you hear rattling on cold start, book an inspection immediately. A preventative chain and tensioner replacement is far cheaper than a full engine replacement.

Read the full timing chain failure guide

4. M157 Cylinder Scoring (C218)

Symptoms: Misfire, low compression, excessive oil consumption, engine warning light, rough idle, blue smoke

Typical mileage: 50,000–90,000 miles

Repair cost: £2,000–£4,000 (cylinder bore inspection and assessment)

Replacement cost: £5,500–£9,000 (if scoring requires engine replacement)

🟠 Check - book inspection urgently

Our recommendation:

The M157 can suffer from cylinder scoring, particularly on cylinders 1 and 5 due to their proximity to the turbos. The issue is more common on tuned cars. If you notice misfire, oil consumption, or blue smoke, have a compression test and boreoscopy performed. Prevention includes regular oil changes with 0W-40 (MB 229.5) and avoiding hard driving before the engine reaches operating temperature.

Read the full cylinder scoring guide

5. Oil Wicking into Engine Harness (M156 & M157)

Symptoms: Various electrical faults, engine warning light, erratic sensor readings, ECU failure

Typical mileage: 40,000–100,000 miles

Repair cost: £500–£2,000 (harness cleaning or replacement)

Replacement cost: N/A — repair only

🟠 Check - book inspection urgently

Our recommendation:

Oil can leak from camshaft sensors and wick through the wiring harness to the ECU, causing electrical faults. This affects M156, M157 and other Mercedes V8 engines. Check the engine harness for oil contamination. If you experience electrical gremlins, have the harness inspected.

Read the full oil wicking guide

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CLS63 AMG — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

CLS63 AMG — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseM156 head bolt failure (pre-2011)✅ Yes£1,600–£5,000Essential upgrade — far cheaper than a full engine replacementM156 camshaft/lifter wear✅ Yes£2,000–£4,500Catch early; cheaper than a full engineM157 timing chain stretch (early)✅ Yes£2,500–£5,000Labour-intensive but cheaper than a full engineM157 cylinder scoring⚠️ Sometimes£2,000–£4,000If severe, replacement is the only optionM157 turbocharger failure✅ Yes£2,000–£4,000Replacement — catch before debris damages the engineOil wicking into harness✅ Yes£500–£2,000Harness cleaning or replacement

Buying This CLS63 AMG? Check These First

Buy If

C218 (2013+) with updated M157 components — later cars benefit from improved timing chain components
C219 (2011+) with revised head bolts — the defining weakness addressed
Evidence of regular oil changes (every 5,000–10,000 miles) — all AMG V8s are unforgiving of neglect
Documentation of timing chain work on early M157 cars
7G-Tronic transmission service history — valve body issues can occur on higher-mileage cars

Avoid If

C219 (pre-2011) with no proof of head bolt work — you're buying a known risk
Any ticking from the top of the engine on M156 — camshaft/lifter wear is likely
C218 (2011–2012) with no proof of timing chain work — early M157 chain stretch is common
M157 with misfire codes and no diagnosis — cylinder scoring is possible
Poor service history — these engines are unforgiving of neglect

Closing Verdict

The CLS63 AMG is a genuine performance icon across both generations. The C219 M156 (2006–2011) is a naturally aspirated masterpiece with well-documented head bolt and camshaft issues. The C218 M157 (2011–2017) is a twin-turbo V8 with its own weaknesses — timing chain stretch (early cars), cylinder scoring, oil leaks, and oil wicking. The M157 is generally more reliable than the M156 when maintained properly. Both engines are complex and expensive to repair — buy on history, maintain on schedule, and any CLS63 will reward you with one of the most engaging driving experiences available.

Don't guess.Get the right engine at the right price.

→ Compare CLS63 AMG engine prices before you buy

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Buying Checklist

Before you buy a used Mercedes-AMG CLS63 (or before you commit to an engine replacement), check these:

1. Engine Number (C219) — Check if head bolts have been revised

2. Cold Start — Listen for rattles from the front/top of the engine (M156: camshaft/lifter wear; M157: timing chain stretch)

3. Service History — including which generation (C219 or C218) and evidence of major maintenance

4. Coolant Level — Any unexplained loss? (M156 head bolt or cooling system warning)

5. Misfire Codes (M157) — Any stored codes? (cylinder scoring warning)

6. Oil Leaks — Any oil under the car? (M156 valve cover gaskets; M157 cam sensors)

7. Oil Level — Is the oil level rising? (coolant mixing with oil — head bolt failure warning)

8. Transmission — Any rough shifting or delayed engagement? (7G-Tronic valve body issues)

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Engine Codes

This table's rows match Section 1B's Era Map exactly — two engine families across the CLS63's history.

M156.983

Years2006–2011

Power514 hp

2025 Enquiries[PATTERN DATA]

Avg. Recon Cost£4,500–£8,000 [MB-QUOTE]

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

M156.9832006–2011514 hp[PATTERN DATA]£4,500–£8,000 [MB-QUOTE]

M157.9812011–2014525–557 hp[PATTERN DATA]£5,500–£9,000 [MB-QUOTE]

M157.9812013–2017585 hp[PATTERN DATA]£6,000–£10,000 [MB-QUOTE]

Technical Specs

M157 — 5.5 Biturbo V8

Displacement6,208cc (6.2‑litre)

CylindersV8, 90° configuration

Bore x Stroke102.2 mm x 94.6 mm

Compression Ratio11.3:1

Fuel SystemMulti-point fuel injection

ValvetrainDOHC, 4 valves per cylinder, duplex roller chain

Displacement5,461cc (5.5‑litre)

CylindersV8, 90° configuration

Bore x Stroke98.0 mm x 90.5 mm

Compression Ratio10.0:1

Fuel SystemDirect injection (piezo injectors)

TurbochargerTwin-turbo

Oil Capacity8.5 litres

→ Compare CLS63 AMG engine prices for your Mercedes

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Market Intelligence

Most Common Failure

M156: Head bolt corrosion (pre-2011) and camshaft/lifter wear / M157: Timing chain stretch (early) and cylinder scoring — the defining risks of each generation

Average Enquiry Mileage

M156: 50,000–90,000 miles / M157: 40,000–80,000 miles【PATTERN DATA】

Average Replacement Cost

M156: £4,500–£8,000 / M157: £5,500–£10,000 reconditioned, supply only

Most Requested Engine Code

M157 — the twin-turbo V8【PATTERN DATA】

Peak Enquiry Season

Spring — performance car season【PATTERN DATA】

Regional Demand

London22%

South East18%

South West (14%)【PATTERN DATA】

Regional Demand Breakdown

22%London

18%South East

Frequently Asked Questions

All prices are indicative UK market ranges based on historical quote data from our network of engine specialists. Actual costs vary by variant, engine code, damage severity and workshop location. Use our free comparison tool to get tailored quotes. Every engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty — always confirm terms with your chosen supplier.

Trusted CLS63 Engine Suppliers
every garage and engine rebuilder in our network is vetted, rated and reviewed by real CLS63 AMG owners, as part of the Engine Finders network, across both the M156 and M157 generations — no matter which V8 era your CLS belongs to.
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see prices, warranty terms and supply & fit options side‑by‑side before you commit, with specialists who genuinely understand the M156's head bolts and camshafts, and the M157's timing chain, cylinder scoring and oil wicking nuances.
UK Engine Replacement Services for CLS63 AMG
supply‑only or full supply & fit available nationwide, covering Mercedes-AMG's four-door coupe V8s with a 12‑month warranty as standard.

Find the best Mercedes-AMG CLS63 engine replacement UK owners trust. Compare prices from trusted specialists on MercedesEngine.uk today and keep your CLS63 performing at its best.

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